valuable for habitation or culture, the danger rather lies in the other extreme, that the country will become so denuded of forests as to render the climate too dry for the profitable pursuit of agriculture. This has, in fact, taken place of late years to so great an extent as to demand the most serious attention. In many parts of the continent of Europe great efforts are now being made to restore a portion of the forests which have been ruthlessly destroyed. At one Government establishment in Dalmatia five million young trees are now in cultivation for this purpose. In our Indian possessions the evil resulting from the destruction of the forests reached some years ago so gigantic a dimension as to demand the instant interference of the Government. The Indian forests are in themselves a source of great revenue, producing the most valuable teak, and multitudes of the more ornamental woods used in cabinet-work. But, independently of this, the most injurious consequences had resuited to the climate from their wanton destruction; the droughts, becoming constantly more frequent and of longer duration, brought terrible famine in their rear; and the swollen water-courses, when the main did come, caused fearful devastations. The Government at length took the subject up, and in all our Indian Provinces the Conservancy of Forests is now an important branch of the Administration, though much yet remains to be done in consolidating and perfecting the system. In Mauritius similar results have followed similar causes. The fertility of the island has been diminished by the destruction of the forests; and the fever which a few years since decimated Port Louis is attributed to the malaria occasioned by the floods brought down by the torrents swollen far beyond their ordinary dimensions.

The literature of Forest Conservancy is, in fact, now enormous. The standard work on the subject, as far as India is concerned, is by Dr. Cleghorn,* the Conservator for the Madras Presidency, which gives a history of what our Government has been doing there. We are constantly receiving, however, from others of our colonial dependencies, official reports of the efforts being made in them for the preservation of the native forests; and it is impossible in this connection to avoid mentioning the name of Ferdinand von Mueller, the accomplished Curator of the Botanic Gardens at Melbourne, whose exertions in the introduction and acclimatisation of Australian forest trees in other climes have been unwearied and of inestimable value.

In Algeria the same tale is told as in India. Up to about the year 1865 the wanton destruction of the forests by the Arabs by fire and other means, was enormous; until at length the French Government took up the subject, ably aided by one or two English and French owners of land in the Colony. The tree found there most efficacious in repairing the waste, is not a native, but one of the family known in Australia as "gum-trees," the Eucalyptus globulus of Tasmania. The great advantage of the planting of this tree is, not only the value of its timber, but its prodigiously rapid growth, said to be fully twenty times greater than that of the oak. It has been introduced also with great success into the South of France, owing to the energy and enterprise of v. Mueller, and is hardy in this

***The Forests and Gardens of South India." By Hugh Cleghorn, M.D. F.L. S. (London: W. H. Allen and Co., 1861.)

country. The foliage is said to secrete a gum-resin, which acts as a most valuable antidote to malaria fever.

In the French department of the Hautes Alpes, an interesting experiment has been tried of a somewhat different character. The same results had there ensued from the same causes. Year by year the mountain villages had been abandoned, and in twenty years a diminution of population to the extent of 11,000 had taken place. An attempt to replace the forests met with the most violent opposition from the peasantry, and they were allowed to substitute "gazonnement" for "reboisement;" that is, the people were compelled to returf the barren and neglected districts. The effect is said to have been most beneficial. The fresh covering of the naked soil has prevented evaporation, and has allowed the rain to sink in instead of running off in destructive torrents; and districts which a few years ago were abandoned to desolation are now gradually acquiring a luxuriant vegetation, and giving food and shelter to the flocks and herds which had long been strangers to them; the streams are becoming clearer and less violent, and the bridges are no longer periodically carried away.

There is probably no department of Science to which human energy and ingenuity could be more profitably turned than the reclaiming of the waste places of the earth.

DANA ON CORALS

Corals and Coral Islands. By James D. Dana, LL.D. &c. (Sampson Low and Co., 1872.)

THE

THE distinguished naturalist, geologist, and mineralogist, who is the author of this semi-scientific work, is probably, next to Charles Darwin, the man from whom an expansive book on coral formations would be expected. He has had immense opportunities for the careful investigation of all the phenomena of coral reefs, and his peculiar mental constitution has assisted him in all his endeavours to teach and to arrange. No geologist has equalled Dana in the arrangement of his work; and his celebrated book on that science is eagerly studied by teachers of all degrees. As a student of details, he may point to his Mineralogy with great pride; yet, with these powers and gifts ready at hand, Dana produces, late in life, this disappointing. book. It is full of precious stones in ugly settings, and the gems are intermixed with much that is worthless. To the general public it will be almost a closed book for years and it is hardly worthy of a place in a purely scientific library. A great portion of the book is taken up by descriptions and remarks upon animals which are not corals, and which in no way affect or produce coral reefs or islands, and the old errors respecting coral productions are perversely introduced. All the notices and descriptions of the Actinic and Hydroidea might have been omitted, as they only confuse the subject, and surely such statements as refer coral making to (1) Polyps, (2) Hydroids, (3) Bryozoa, (4) Algæ, might have been left buried in the memories of those who have been teaching that the third and fourth named organisms have nothing to do with coral any more than oysters and sunflowers.

Writing about Actiniæ, Dana gives the following without reference :-" As to senses, Actiniæ, or the best of them, are not so low as was once supposed; for, besides the

general sense of feeling, some of them have a series of eyes placed like a necklace around the body, just outsid: of the tentacles. They have crystalline lenses, and a short optic nerve. Yet Actiniæ are not known to have a proper nervous system; their optic nerves, where they exist, are apparently isolated, and not connected with a nervous ring such as exists in the higher radiate animals." Now, the "bourses marginales" have highly refractile cells and elongated cells without nematocysts associated with them; then a mass of granular and opaque tissue separates them from some irregularly-shaped cells which are not peculiar to the spot, but which are found between the muscular layers also. Corresponding refractile cells are to be found on the tentacles. We have followed Schneider in these researches, and do not as yet feel disposed to recognise an optic organ.

The classification of the corals employed by Dana is, as might have been expected, not that followed by those men who have raised those Radiata from the Slough of Despond in which they were left by the predecessors of Lamarck. The introduction of American novelties, to the exclusion of well-recognised European classifications, is neither right nor scientifically correct. For instance, Dana mentions the "Oculina tribe, or Oculinaceæ," and, after giving his differentiation, proceeds: - "The Orbicella is an example of one of the massive Astræa-like forms constituting the Orbicella family, or Orbicellidæ, in the Oculina tribe. The Caryophyllia here figured (Caryophyllia Smithii, Stokes) is one of the solitary species of the tribe found in European seas and on the coast of Great Britain." "The coralium of an allied species (Caryophyllia cyathus)," Dana proceeds to inform us, is found "not only in the Mediterranean, but also over the bottom of the Atlantic, even as far north as the British Isles." "Another example of this tribe, as defined by Prof. Verrill, is the species of Astrangia occurring a'ive along the southern shores of New England, and on the west of New Jersey." The diagnosis of the Oculina tribe was the growth of the experience of Schweigger, and of Milne-Edwardes, and Jules Haime, and they separated the incongruous genera which Lamarck had associated with it. The admission of Orbicella, which is really the old Astræa of Lamarck, and of Caryophyllia into this welldifferentiated tribe, is simply absurd, for they possess structural characters sufficiently diverse as to place them in different families. The discovery of Caryophyllia Smithi in the European seas was due to the investigations of the results of the late deep-sea dredgings of H.M.S. Porcupine, and those unrecognised workers have shown that it is not Caryophyllia cyathus, but C. clovus, which has the great horizontal range. Had Dana waited a little longer he would have had the opportunity of quoting correctly. Again, Astrangia was well differentiated long before Prof. Verrill was heard of. The American Conrad, and our Lonsdale, and finally, the distinguished French Zoophytologists, for whose labours our author appears to have a supreme contempt, inasmuch as he rarely gives them credit for their good work, consolidated the genus, which has nothing in common with the Oculinidæ.

Interesting and valuable chapters on the distribution of corals according to temperature, and on their limitation to certain areas, follow. Darwin is supported in his views of the 20-fathom range of reef-building corals, and some interesting data are given respecting the rapidity of growth

of corals. A madrepore is stated to have grown 16 feet in 64 years; but the rapidity of growth depends upon the habit of the species, the freedom from the destructive effects of boring mollusca, nibbling fish, and wave-breaking, and is, under favourable conditions, very rapid. The chapters on the strictures of coral reefs and islands add little to the knowledge which Darwin and Jukes and Hochstetter have given us; but Dina's great powers of illustration enable him to reproduce the details with which we are so familiar, thanks to these authors, in very engaging forms. He tells us, however, that in the reef, "The coral d'bris and shells fill up the intervals between the coral patches and the cavities among the living tufts, and in this manner produce the reef deposit, and the bed is finally conso'i lated while still beneath the water."

Noticing, then, the great power of the force of sea wave in smashing and removing masses of coral, and the effects of the passage upwards on to the beach of hard blocks in destroying and comminuting smaller zoophytes, Dana very properly insists upon the formation of what are usually called coral islands, from the collection of beached coral boulders, and suggests that the extreme grinding and pounding of the most fragile coral stems places the carbonate of lime, of which they are conposed, in the best position for solution in highly aërated sea water. He notices the formation of mud in and about the reefs, and compares its origin to that of any other kind of sand and mud. "It takes place on all shores exposed to the waves, coral or not coral, and in every case the gentler the prevailing movement of the water the finer the material on the shore. In the smaller lagoons, where the water is only rippled by the winds or roughened for short intervals, the trituration is of the gentlest kind possible, and moreover the finely pulverised material remains as part of the shores." He shows that the particles of the very fine mud which is washed out from the beach sands accumulate only in the more quiet waters some distance outside of the reef, and within the lagoons and channels where it settles.

After remarking upon the abundance of fish around coral islands, especially in the instance of Taputenea, with an area of six square miles, whose population of 7,000 is supported by fishing, Dana notices the drifting of logs of wood on to remote islands. "An occasional log drifts to the shores, at some of the more isolated atolls, where the natives are ignorant of any land but the spot they inhabit, they are deemed direct gifts from a propitiated deity. These drift logs were noticed by Kotzebue at the Marshall Islands, and he remarked also that they often brought stones in their roots. Similar facts have been observed at the Gilbert Group and also at Enderby's Island and many other coral islands of the Pacific. The stones at the Gilbert Islands, so far as could be learned, are generally basaltic or volcanic, and they are highly valued among the natives for whetstones, pestles, and hatchets. The logs are claimed by the chiefs for canoes." These waifs and strays, and others, like the large masses of "compact cellular larvæ" lying 200 yards inside of the line of breakers on Rose Island, and the fragments of pummice and resin which, transported by the waves, are collected by the natives on their shores, are very interesting and suggestive to the botanist, mineralogist, and archæologist-more so, per

haps, than to the natives, who are not admired by Dana, for they evidently lead too carnal an existence, and care little for poesy and the imagination.

After explaining the origin of gypsum in some of the smaller completed atolls by evaporation of sea-water in the gradually drying lagoon, Dana describes some of the guano deposits which collect on the coral limestone and sa'ine mud, and mentions how these accidental additions with the stones and drift wood, explain many difficult geological and mineralogical problems. "Some interesting pseudomorphs occur buried in the guano of Baker's Island. Coral fragments of various species were found that had long been covered up under the deposit, and in some of which the carbonic acid had been almost entirely replaced by phosphoric acid. On such I have found 70 per cent, of phosphate of lime." This is an interesting fact, especially when it is remembered that birds' dung may have collected in all climates during many geological ages. The descrip.ion of the geographical distribation of coral reefs is followed by a most interesting chapter on changes of level in the Pacific Ocean. The irregularity of the elevations and subsidences, even on confined areas, is admirably demonstrated. The formation of compact white limestones, and of impure or argillaceous limestones, and of beach or sand-drift rocks and oolitic limestones, is explained, but without reference to the admirable researches of Nelson, whose labours in the Bermudas are classical amongst European geologists. Then there is a sweeping assertion that deep-sea limestones are seldom if ever made from coral island or reef débris, and that lands separated by a range of deep ocean cannot supply one another with material for rocks. The words "deep sea" are now differently understood to what they were in the days when theoretical views of the depth took the place of the results of real measurements, so that it is necessary to assert that abyssal seas may prove such barriers. But research into the lithology of the Atlantic near the Azores distinguishes mineral matters which, in all probability, are of American origin; and both in the Miocene deposits of the West Indies, and in those of the same age in Europe, there are proofs of the enormous aggregation of coral debris in deep limestones. Dana considers that the views, so ably put forward by Lyeli and many American geologists concerning the derivation of the sedimentary rocks of the Appalachian strata from land to the east- that is to say, to the area of the present Atlantic-are unsound, because the wreck of the hypothetical continent could not have passed along the floor of the deep intervening sea. He states that the Atlantic would get back all its own dirt-an observation which would be trenchant enough, if geology did not prove the extraordinary distances to which sediments were removed from their sources.

raised reef in Oahu, near Honolulu, but which contained no traces of Foraminifera, is succeeded by essays on oceanic temperature and oceanic coral island subsidence. The Gulf-stream is stated to have had, from the Jurassic period in geological history onward, the same kind of influence on the temperature of the North Atlantic Ocean which it now has; and the British oolitic reefs are quoted as substantiating this assertion. Certainly during the Miocene the isthmus of Panama was under water, and vast tracts of the north of South America, and of the south of North America, and therefore the existence of a Gulf stream at that time may be doubted. Then there were stupendous reefs in the Italian and Austrian area, and the influence of anything like a Gulf stream would have had no effect upon them.

After noticing that coral islands are evidences of buried lands, Dana insists that "we are far from establishing that these lands were oceanic continents. For as the author has elsewhere shown, the profoundest facts in the earth's history prove that the oceans have always been oceans." This dictum is constantly in the mouths of some geologists, and its value may be appreciated by the remembrance that the existing continents are mainly composed of old sea, deep sea, and abyssal floors, and that very probably there has always been a comparatively exact relation between the amount of land and sea on the earth's surface. Moreover, there are very strong reasons for believing in a former Atlantis, and in a continent or a series of great islands between South America and New Zealand.

The illustrations of the book are numerous, and some of them are very correct representations of nature. The group of Caryophilliæ in page 42 is excellent, but British aquarium-keepers will hardly recognise the well-known Carophyllia Smithii on page 67. Many of the white etchings on the black ground are beautifully executed, and copies of them will make excellent diagrams.

OUR BOOK SHELF

P. M. D.

Bird-Life. By Dr. A. E. Brehm. Translated from the German by H. M. Labouchere, F.Z.S., and W. Jesse, C.M.Z.S. Parts iv. and v., 1872. (London: Van Voorst.)

THIS is a translation of a work well known in Germany, where it has attained great and in some respects merited

success.

"Das Leben der Vogel" is the production of one of a talented family, who have done much to popularise several branches of natural history. We do not say that it was not worth translation, but we do affirm that the translation is not worth half-a-crown a numberthe price at which it is issued in this country-even when the value of Mr. Keuleman's nicely tinted lithographs is taken into account The idea of Brehm's book is to give general and on particular occasions In the parts of the a popular account of the way birds pass their lives in translation now before us the chapters relate to the "every-day-life," "courtship and marriage," "nest-building," and "migration" of birds. These are all described nicely enough, the author being an excellent field naturalist, and with sufficient accuracy, though in a very desultory manner. Anecdotes are often given from other

An interesting notice of the occurrence of chalk in a

which has been extensive. But the work is a mere sketch of a history which it would occupy many volumes to

The

water

THE river basins to which this little book refers are those of Great Britain and Ireland, and the notes are published, the author says, in the hope that they may be found useful to pupil-teachers. They are intended to form a supple. ment to the usual text-books of school geography. rivers of England are given first, then those of Scotland and Ireland, each system being preceded by a general sketch of the course of the water-shed (or parting," as Mr. Williams prefers to call it) of the country to which it belongs, and followed by a section on the canals. The author commences at one end of each country, takes the rivers in their order round the coast, names the drainage basin and source, describes the course and mouth, takes up and describes each tributary and affluent as it occurs, names and gives the measurements of any lakes which may be in the way, mentions the most remarkable features, and ends by giving the length of the main river and the area of its basin. So far as we have tested it the information seems in the main accurate, and the list of rivers and tributaries is remarkably full. Mr. Williams mentions the fall of the Rumbling Bridge on the Devon, a tributary of the Forth, but takes no notice of the equally high and equally grand fall of the same name on the Bran, a tributary of the Tay. It is surely very unusual to spell Dunkeld "Dunkield." The book will be useful to all who wish to have the main details concerning British rivers and canals carefully and clearly arranged in a handy form.

LETTERS TO THE EDITOR

IF the following translation of a letter I have received from Father Denza, Director of the Royal Observatory at Montcalieri, in Piedmont, will be of interest, it is at your service.

R. P. GREG

"Dear Sir,-A great shower of luminous meteors has just been witnessed throughout this country, and has no doubt been observed to fall continuously until midnight, and had it not then seen elsewhere. As soon as it became dusk falling stars were become cloudy no doubt they would have been seen until a still later hour. About 33,400 meteors were here counted by four observers. Even this number does not adequately represent the probable actual numbers. About 8 P.M. (when in some parts of the sky there seemed a real rain of fire) it was difficult to keep count, especially of those meteors appearing near the zenith; and at one time our four observers counted on the average 400 meteors every minute and a half. All the wonderful and beauti ful appearances reminded us of the November shower. The meteors appeared of various colours; some left brilliant streaks; fireballs were frequent, some with an apparent diameter nearly equal to the moon's; some here and there breaking up in a thousand ways, as into a luminous cloud, or opening out into bundles of rays of singular shapes. From time to time some of these nebulous trains or appearances pursued their courses; or now vanishing or halting, only again to reappear. One of these, which appeared at 6h. 35m. between Perseus and Auriga, remained visible until 6.56, or 21m. after its first becoming visible. In short the general aspect of the phenomenon was that of a cosmic cloud which, encountering our atmosphere, appears and then melts away. The position of the radiant, which was accurately determined, was almost close to y Andromedæ, and the epoch of the appearance induces one to suppose that the meteoric stream which we have just been traversing, and which in fact has been more or less seen every year, though with much less intensity might be the same which was seen by Brande, December 7, 1798, and again noticed on the same

The late Meteoric Shower

WE have had here, and I presume you also have had in England, quite a fine display of shooting stars from the fragments or companions of Biela's co met.

On Sunday evening, Nov. 24, they were coming about as fast as in the thickest parts of the August sprinkles-that is, forty or fifty to the hour, for a single observer. Three-fourths of them radiated from y Andromeda and vicinity.

On Monday morning there was no special abundance, but the radiant was then quite low in the north-west.

Monday evening they were coming with about half the frequency of the previous evening. Half of those seen came from the Andromeda radiant.

Tuesday evening the sky was overcast, but Wednesday evening there was so great a display as to attract the attention of multitudes. Our party of from two to six persons counted 1,000 in a part of the first hour-that is, from 6h. 38m. to 7h. 34m., and in the next hour and a quarter we counted 750. The display was rapidly diminishing. Before midnight it was essentially over, and, so far as I know, has not re-appeared.

The flights were slower than those of the Nov. 14 period, and generally faint. The radiant was carefully observed on Wednesday evening by Prof. Twining and myself, and we argued that the centre was in the line from the Pleiades to y Andro. med produced, and was about 3° beyond that star.

It

was much longer in right ascension than in declination, and was not less than 8° long. The star was within the radiant area, for flights in the several directions from the radiant would, if produced backward, pass sometimes on one side and sometimes the other of that star.

The character of this display, and the previously observed divi.

Flangergnes; later again in 1847 by Prof. Heis, of Münster; and in 1867 was recognised by Signor Zerioli at Bergamo. At the present time its point of contact with the earth's orbit must have taken place on November 27-28. Now it results from sufficiently probable calculations, that this meteor stream marks the orbit of the so much celebrated comet of Biela, the appear. ance or passage of which we have been expecting in the month of October of the present year, and for which astronomers are on the look-out. Most probably the large meteoric stream or cloud which produced this remarkable shower of falling stars last evening belongs to a part of this comet; so much the more likely when we consider that only yesterday the earth passed through one of the two nodes of this comet's orbit.

"A fine rose aurora was visible last evening from 6 to 8 P. M., adding to the beauty of the entire phenomenon. "Yours respectfully,

"DENZA

"Montcalieri Observatory, Nov. 28, 1872 "P.S.-The shower was seen by many other Italian observers and astronomers-by Gasparis at Naples, who noted two meteors per second; Prof. Eugenio at Matera with three assistants counted 38, 153 meteors between 6 and 12 o'clock; at Messina the number was too great to count; at Mandori Prof. Bruno and three assistants counted 30,881 meteors between 6h. 18m. and 14h. 15m.; at Ancona were counted 5,000 meteors per hour. The maximum appearance generally at all these stations was about 8 P.M., and the radiant was found to be not far from 7 Andromeda."

WHILE going to the Naval Observatory on the evening of November 27, I noticed many shooting-stars, and made the follo wing observations :-From 6h. 25m. to 6h. 43m., Washington mean time, I counted one hundred meteors; and from 7h. 40m.

to Sh. om. I counted fifty meteors. The observer's face was north-west. The sky was clear to within ten or fifteen degrees of the horizon. The meteors were generally very small, and I noticed only four or five near the zenith that left trails behind that endured a few seconds. In one respect the meteors were remarkable: they all appeared to radiate from a point between the great square in Pegasus and the chair in Cassiopeia, so that during my two watches I saw but a single meteor that could properly be called sporadic. By laying down some of the tracks on a globe, I found the following rough position of the radiant point:

AR = 355°, Decl. = + 43°.

From this position of the radiant point I have computed the following elements of the orbit of the meteoric stream, and by the side of these have placed the corresponding number of Biela's comet :

π

Ω i

=

=

log 4 =

These elements are so much alike, that there can be but little doubt that the meteors are the transformed particles of Bicla's comet. ASAPH HALL

Washington, Dec. 1

ON the evening of November 27, Prof. Tingley, of Asbury University, Greencastle, Indiana, observed a remarkable shower of falling stars. The number counted in 40 minutes, from 7h. 15m. to 7h. 55m., was 110. This would give 165 per hour for one observer. But according to Prof. Newton (Sillimen's Journal, for January 1868, p. 80), the whole number visible at any station, when the sky is entirely clear, is five times the number seen by a single observer. The enumeration by Prof. Tingley accordingly indicates an actual fall of 825 per

THE aurora of Nov. 27-the evening of the meteoric displaywas seen by me near Liverpool. It appears to have been very partial in its manifestation, to judge by the published accounts. There was merely a hazy or diffused cloudy light, devoid both of colouring and symmetry of form. This variety of aurora I have observed on several occasions, when it appears to have attracted but few observers.

I may draw attention now to the fact of another display of aurora on Nov. 10 (noticed first at about 11.20 P.M.). This was of the usual form, ruddy, and radiating from a horizontal band of light in the north. It was followed by a week of much colder weather than had preceded it.

Liverpool, Dec. 13

SAMUEL BARBER

As the number of meteors which I counted on the evening of Wednesday last, November 27, varied considerably from the number in Mr. Lowe's tables (Times, November 29), I beg to offer you my observations, in case they should be of any value on account of the more southern point from which they were taken. I lay down on my back upon the flat roof of the house in which Meteoric Astronomy," p. 55.

10 24 29

Between 8 and 8.30, a friend and I counted together about 50 per minute. J. F. ANDERSON Pau, Dec. 2

The Ocean Rainfall

ON reading the article on "The Meteorology of the Future," in NATURE, December 12, I pondered over this passage-" It is impossible to determine the rainfall over the ocean; and it occurred to me that it is possible to do something in that line approximately. Is the Challenger supplied with raingauges? Would it not be possible to determine in some measure the hourly amount of rainfall over the ocean, in the zones of greatest precipitation, or in those of periodical rains, without detaining the ship unduly; and would not such data be useful in solving some of the problems connected with the working out of the law of cyclones?

Another suggestion has occurred to me-that is, that raingauges might be placed in "floating lights," and the rainfall at sea thus obtained. I need not now inquire through what channel this might be effected, or what particular structure and fixing of the gauges might be necessary. I should be glad to elicit the opinion of some of the readers of NATURE as to the practicability and utility of such a scheme. ¡ S. H. MILLER Wisbech, Dec. 14

Ocean Meteorological Observations AN examination of the discussion of the daily range of the barometer for square No. 3, published under Fitzroy's direction in 1861, which Mr. Symons has referred to at page 68 of this volume, shows that the results there arrived at can only be considered to be good as corrections for hourly observations of the barometer on the mean of the year. As regards the months, the results are, on account of the fewness of the observations on which they are based, too imperfect as indications of the true range to be available in correcting the averages on the large January chart issued by the Meteorological Committee. Since, moreover, the barometric range for January differs from that for the year, the hourly corrections for range on the mean of the year should not be applied to the January observations printed on the large chart.

Again, the prevalence in January of the south-easterly trades in the southern portion of the square, the prevalence of the north-easterly trades in the northern portion, and variable winds between, and the unequally clouded state of the sky which results therefrom, render it certain that range corrections must