cupboards, they are little more assorted than the plants which constitute a haystack. A considerable part, if not the whole, of the 7,000 specimens of plants from the expeditions of Hooker and Thomson, which cannot have been received less than fifteen years ago, were, quite lately, still unmounted and unincorporated. Again, merely to quote instances which have come unsought within my own observation, the plants collected in Nepaul half a century since by Wallich, and as I learn from a distinguished Indian botanist, in a district which has never since been botanically explored, were recently, and perhaps are still, amongst the unarranged collections. These altogether, I should judge, roughly form in bulk about one-sixth of the whole herbarium. The arranged portion is estimated to possess 77,400 species of flowering plants, contained in 306 cabinets with 8 shelves; the Kew Herbarium, on the other hand, possesses 105,000 to 110,000 species in 450 cabinets, on an average of 16 shelves. As I have ascertained that the shelves are in each case about the same width apart, and about equally filled, these figures give roughly three times as many shelves to the Kew Herbarium, and somewhat less than half as many more species.

There can be no doubt, therefore, that the British Museum Herbarium might be materially developed, especially when it is remembered that Mr. Bentham's herbarium, when presented to Kew, contained between 60,000 and 70,000 species, and that this was formed in less than forty years by a single individual. The examination of the unarranged collections in the British Museum would, no doubt, yield a large number of duplicates, and these should be exchanged with foreign herbaria. If this were done-and there is no reason why the appliances of Kew should not be utilised for the purpose-it would be easy, without interfering with the independent action of either establishment, to bring about for the future a mutual interchange of specimens. Nor is there any reason why, when needful, the type specimens of the older botanists should not be lent to Kew from the other Herbarium, considering that both are Government property.

In

The development of the botanical collections in the rooms open to the public at the British Museum into something more useful, educationally, would probably be achieved by the officers, if they possessed more space. this case it would be very desirable to transfer to them the collections belonging to vegetable palæontology in the Geological department. At present the nucleus of a collection of fossil plants bequeathed to the Botanical department by Robert Brown is being gradually developed, so that there are now actually two distinct collections, both having the same object, and existing independently of one another, and in charge of different officers, in the same building. W. T. THISELTON DYER

THE RAINFALL AND TEMPERATURE OF NORTH-WESTERN EUROPE

THE Scottish Meteorological Society have just received letters from their observers in Iceland and Faroe, together with the regular observations made by them for the Society to the end of November last, which are of interest in connection with the unprecedentedly wet and changeable season we have had in Scotland and elsewhere.

The rainfall in Iceland this year to the end of October has been 484 inches under the average of the ten months, the deficiency occurring chiefly in January, February, July, September, and October. In Faroe the deficiency has, to the end of November, amounted to 1100 inches, the dry months being February, 4'50 inches under the average; July, 109 inch; August, 2'97 inches, and November, 4'17 inches. In Scotland, February was everywhere a wet month, except in the northern and western islands and in Clydesdale; and September, October,

and November were very wet months,--all these months being characterised by a small rainfall in the north. The mean temperature at Stykkisholm, in the northwest of Iceland, was 337 in January, or 6°8 above the average, being the highest mean temperature recorded in January since 1846, except that of 1862, which was 1oo higher; 5207 in July, and 51°6 in August, being respectively 36 and 3°4 above the average of these months and the highest that has occurred since July 1847 and August 1846. And as June was oo6 and September 10 above the average, the past summer has been one of the finest experienced in Iceland for many years. The temperature in April was 3°5, in May 14, and in October 10 under the average. On the other hand, the temperature of Faroe closely agreed with that of Scotland during the year, viz., above the average in January, February, March, April, June, July, and November, and under the average during the other months, especially September.

At Melstadt, on the north coast of Iceland, the summer was very fine, but in the beginning of October the weather broke, and on the 13th the temperature fell to 3°0 or 29°0 below freezing. At Reykjavik, the summer was also fine, but the autumn was remarkable for north and north-east gales, frequent auroras, low sea temperature, and large amount of ozone. Along with the unusual manifestation of these phenomena, inflammatory diseases were prevalent, especially bronchitis, catarrh, croup, and diphtheria. The temperature of the sea presented certain very interesting anomalies during the year. In the earlier months it was, equally with the temperature of the air, above the average of former years in Iceland, Faroe, and Scotland. But at Stykkisholm it was 2017 in May, and 4o*2 in June below the average, it being at the same time from half a degree to a degree above the average in Faroe and Scotland. On the other hand, the sea was, at Stykkisholm, 208 in August, and 2o6 in September above the average, whereas at Sandwick, Orkney, it was 1°2 and I below it in the same months. In Faroe the temperature of the sea was above the average every month of the year (except October, when it was o°3 below it), amounting during the eleven months to an average excess of 1°.1.

The following are the differences from the averages of the sea temperatures at Stykkisholm from March to October, 1872 :

In May the mean temperature of the sea was 367, and in August 53°1. So great an increase as 176 has not been previously observed in these months.

It is also a noteworthy circumstance that the means of the nine months' barometric pressure, from February to October, at Stykkisholm, have been in every case above the average, amounting to an average monthly excess of o'118 inch. In Norway also, from February to August, to which the observations have reached us, the means were every month above the average, amounting at Vardoe (lat. 70° 20') to a mean monthly excess of o 260 inch; Christiansund, o'129 inch; Christiania, o'151 inch; and Maudal, near the Naze, o'084 inch. On the other hand, barometric pressure was every month from February to October, below the average; at Paris, and in Guernsey, the mean monthly deficiency being respectively o'074 and o'090 inch. At Greenwich, the mean deficiency for the last nine months was o'083 inch; Glasgow, o'091 inch; Edinburgh, o'088 inch; Aberdeen, 0072 inch; Culloden, near Inverness, o'34 inch; and at Stornoway, the station nearest to Iceland, only o'006 inch. This high barometer in Iceland and Norway has had an important bearing on the unprecedently wet weather, and the accompanying low barometer we have had south of that region.

ALEXANDER BUCHAN

IN

ON THE SPECTROSCOPE AND ITS APPLICATIONS

IV.

N what has now been stated we first saw Newton founding spectral analysis, by using a hole in a shutter and a prism; then we discussed Wollaston's substitution of the slit; after that Mr. Simms' introduction of the collimating lens was referred to; and then the growth of the modern spectroscope.

It is time, now, that we came to the applications of the instrument. And in dealing with these applications I shall divide my subject into two perfectly distinct portions. I shall first deal with those which depend upon the diffeent modes in which light is given out or radiated by

be present. If I were to burn a piece of paper, or a match or an ordinary coal gas flame, you all know we should get a white light, but you may possibly not all know that if we raise any solid or liquid to a state of incandescence or glowing heat we should get exactly that same sort of light, which will always give us a continuous spectrum. Before a large audience the best method of showing this fact is to use an apparatus called the electric lamp, and to pass the current of electricity through two carbon points, which are intensely heated by their resistance to the passage of the current. The spectrum obtained from these points, by means of the dispersion of two bisulphide of carbon prisms, is quite continuous from end to end. Now carbon is a solid, and therefore if we take carbon as an example of a solid or liquid substance in a state of vivid incandescence, and we obtain from these carbon points a continuous spectrum, you must accept that as an indica

D

1

b

H.

FIG.

9- Electric Lamp. various bodies under different physical conditions, with, in fact, the radiation of light. And, in the second place, I shall deal with the spectroscope's story of the way in which white light giving a continuous spectrum is stopped or absorbed by different transparent bodies-with in fact the absorption of light.

The first application of this question of radiation is one cf the most general importance. It enables us to differentiate between solid, liquid, and gaseous substances, and between gaseous or vaporous substances in different stages of pressure. If, for instance, we take a platinum wire and heat it to redness, and examine by means of the spectroscope, the light emitted we shall find that only red rays are visible, then if the wire be gradually heated more strongly, the yellow, green, and blue, rays will become visible, until finally when the wire has attained a brilliant white heat, the whole of the colours of the spectrum will

FIG. 20.-Arrangement of the electric lamp used for rapid comparisons. tion of the truth of what I say, for I have not time to experiment on every solid and every liquid substance. The spectrum is received on the screen, and you see it is continuous, that is to say, there are no breaks, such as those we saw in the figure representing a portion of the solar spectrum on page 167 where the black lines represent the breaks in the solar spectrum which are called the Fraunhofer lines.

Let us then consider this fact established, namely, that solid or liquid bodies, when heated to a vivid incandescence, give a continuous sprectrum without bright lines. Under these circumstances the light to the eye, without the spectroscope, will be white, like that of a white hot poker; if the degree of incandescence is not so high, the light may only be red, like that of a redhot poker. But so far as the spectrum goes-and it will expand towards the violet, as the incandescence increases, as before stated-it will be continuous.

Now, suppose, instead of giving you the spectrum of

bustion due to the greater supply of air from the holes at the bottom. The flame immediately becomes of an intense yellow colour due to the vapour of sodium. In this we have further evidence of the connection between the colour of the light which we get from a vapour and the spectrum of that vapour. It is usual to place the salt to be examined in a platinum spoon, and insert it in the flame, but the utmost constancy is insured by adopting an arrangement of Mitscherlich's shown in the accompanying drawing, (Fig. 24) in which a platinum wick is kept continually moistened by a solution of the salt, generally the chloride, the spectrum of which is required to be examined. You will imagine, à priori, from what I have already said, that as in the case of sodium vapour, the colour of the light is orange, the line of the vapour will appear in the yellow or orange part of the spectrum, and

FIG. 24.-Geissler's tube, showing electric discharge.

you will not be mistaken. For you will see on examining this flame with a spectroscope, that we obtain a spectrum consisting of a brilliant yellow line upon an almost black background; if, however, the flame is observed by means of a very narrow slit, this line will appear double, that is it really consists of two extremely fine lines which are very close to each other, and if the slit be wide the images overlap one another.

If we then pass on to another substance, and take some lithium instead of sodium, we obtain a brilliant carmine tinted flame, which on examination by the spectroscope, is found to give a spectrum consisting of one splendid red, and a fainter orange line. Potassium gives a violet coloured flame, and yields in the spectroscope a red line and a violet line. If, again, we take a salt of strontium, which was one of the ingredients in red fire, it colours the flame crimson, and by the eye the flame can scarcely be distinguished from the colour of the lithium flame, but in the spectroscope there is no possibility of doubt, the spectrum of strontium, consists of a group of several lines in the red and orange, and a fine line in the blue end of the spectrum.

If a higher temperature than that of the Bunsen flame is required the blow-pipe flame may be resorted to; in this, the quantity of air and coal-gas is varied at pleasure, and a very high temperature may be obtained.

We might proceed thus to examine all the elementary substances one by one, but to observe the spectra of the metals, it will be found necessary to use a higher temperature still, and for this purpose the electric arc or spark is employed. If a temperature only slightly greater than that of the blow-pipe flame is used, the spark from an induction coil worked by five Grove cells may be taken as shown in Fig. 21, the Leyden jar not being employed; a few metallic lines will then be seen, and a background consisting generally of bands of light here

and there.

If a higher temperature still is used, the jar may be thrown into the circuit, upon which the spark will become more intense, according to the power of the coil and size of the jar; or the electric arc may be employed. The spectra

thus obtained are much more complex; the spectrum of iron, for instance, when examined at this high temperature, is found to consist of no less than 460 lines, many of which are situated in the green part of the spectrum.

With regard to solid and vaporous bodies, the electric lamp affords a very handy method when properly employed, of examining and exhibiting the spectra of these bodies to large audiences.

But there are a great many gases which the spectroscopist also has to study, and to study with the greatest

tric sparks through a tube containing hydrogen at the pressure of one atmosphere, we shall see that the colour of the incandescent gas is a bright carmine red, the spectrum of which can easily be observed by placing the spark tube in front of the slit of one of the spectroscopes before described. This arrangement is one that is in daily use in many of our laboratories, and it must be borne in mind as being the modus operandi by which a great deal of the work has been done to which I shall have to allude shortly. If again we take a tube which contains hydrogen that has been extremely rarefied, and pass a series of electric sparks through it, instead of having the brilliant red colour, we shall have a pale greenish spark, quite different from the former. This great difference is due to the difference in the pressures of the hydrogen of the two cases.

The two spectra are equally distinct, the red light shows three splendid lines, one in the red, another in the bluish green, and the third in the violet, together with a considerable amount of continuous spectrum, whilst almost the only spectrum which can be obtained in the second case, is a single green line in the same position as the former green line spoken of. There is also this difference which will be observed, that the green line obtained from the tube at the atmospheric pressure is very broad and indistinct at the edges; and that the line as seen from the almost vacuous tube is very thin, comparatively speaking, and perfectly sharp and well defined. If we were to take another tube, with a pressure somewhere between the two already mentioned, it would be seen that this green line was not so wide and woolly as in the tube at one atmosphere, and yet not so sharp and well defined as in the almost vacuous tube. Thus it will be seen that this widening out of the line is due to the difference of pressure. J. NORMAN LOCKYER

THE Vice-Chancellor of Cambridge University has given notice that the election of a Woodwardian Professor of Geology, in the place of Dr. Sedgwick, will be held in the Senate House on Thursday, February 20, at 1 P.M. The Vice-Chancellor and Proctors will receive the votes from 1 to 2.30, when the election will be declared. The stipend attached to the professorship is 500l. per annum.

WE are very glad indeed to hear that renewed and better organised efforts are likely to be made to induce Government to undertake the expense of an Arctic expedition. We have good reason to believe that Sir Henry Rawlinson will address a letter to the President of the Royal Society urging the importance of that body taking a lead in the advocacy of such an expedition, This is as it should be, and we have no doubt if the matter is gone about in a thoroughly well considered manner, a second rebuff will not be experienced. Meanwhile we are glad to learn from an obliging correspondent that Mr. Leigh Smith will proceed on his third voyage of Arctic discovery in the spring. He has a fine strong steamer, the Diana, admirably adapted for the purpose; and will undoubtedly achieve all that can be done in the way of discovery in the Spitzbergen seas, during the season of 1873. For Mr. Smith is a good observer and explorer, and is now becoming a veteran Arctic voyager. In 1871 he made

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the most remarkable voyage in that direction since 1707, discovering a large extent of coast line both on the north and south sides of North East Land. He also attained the highest latitude that has been reached in a ship, except by Scoresby and the Swedes. In 1872 he went out again, and though the unfavour. able state of the ice prevented him from doing much, he succeeded in taking a very important series of observations of seatemperatures at various depths. In 1873 he will again, with better means and in a steamer instead of a sailing vessel, make an attempt to explore the unknown lands east of Spitzbergen, and to attain the highest latitude that skill and perseverance will enable him to reach.

THE Senior Wrangler at Cambridge this year is Mr. Thomas Olver Harding, eldest son of the Rev. Thomas Harding, Wesleyan minister of Whitehaven. Mr. Harding, in January, 1866, gained the first exhibition at the matriculation examination of the London University, and the Gilchrist Scholarship at University Hall. In 1867 he gained the Andrews Scholarship in the degree of B.A., in the University of London; and in 1869 mathematics at University College. In 1868 he proceeded to and 1871 he passed the first and second examinations for the degree of B.Sc., gaining the exhibition in mathematics at each. Last year he was elected fellow of University College. In 1869 he entered Trinity as senior minor scholar in mathematics, and was elected foundation scholar in 1871. Mr. Harding has just completed his twenty-third year. His private tutor was Mr. Routh; his college tutor the Rev. E. W. Blore. The Second Wrangler, Mr. Edward John Nanson, was educated at tained a Minor Scholarship at Trinity College. In July 1869, the Grammar Schools of Penrith and Ripon. In 1869 he obhe commenced reading with Mr. Routh, of St. Peter's College. In 1870 he obtained a Foundation Scholarship. He was Prizeman, and placed in the first class at each of the annual College Examinations. His college tutor was Mr. Blore.

AN alteration has been made in Prof. Tyndall's arrangements. We are now enabled to state that he will leave America on the 5th of next month in the Cuba.

WE are glad to see from the account of the annual meeting of the Anthropological Institute officially forwarded to us, that Prof. Busk has been elected President, and along with him the following strong Council:-Vice-Presidents-John Beddoe, M.D.; J. Barnard Davis, M.D., F.R.S.; John Evans, F. R.S.; Col. A. Lane Fox, F.S.A.; Prof. Huxley, F.R.S.; Sir John Lubbock, Bt., F.R.S. Director-E. W. Brabrook, F.S. A. Treasurer-J. W. Flower, F.G.S. Council-H. G. Bohn, F.R.G.S.; Capt. R. F. Burton; A. Campbell, M.D.; Hyde Clark ; W. Boyd Dawkins, F.R.S.; Prof. P. M. Duncan, 'F.R.S.; Robert Dunn, F.R.C.S.; David Forbes, F.R.S.; A. W. Franks; Francis Galton, F.R.S.; C. R. Markham, C.B.; Capt. Sher. Osborn, C. B., R.N.; Capt. Bedford Pim, R.N.; F. G. H. Price, F.G.S.; J. E. Price; F. W. Rudler, F. G.S.; C. R. Des Ruffières, F. R.S.L.; W. Spottiswoode, V.P.R.S.; E. Burnet Tylor, F.R.S. ; A. R. Wallace, F.L.S.

A WORK of considerable importance, a geological map of Australia and Tasmania, has been recently commenced by Mr. R. Brough Smyth, secretary to the Mining department of the Australian Government, which, when finished, will be of value not only to the colony, but to the whole scientific world. As the Minister of Mines has cordially approved of the work, it is intended to communicate with the Governments of the various colonies, forwarding a draft of the map after it has been partially completed from the sources at hand, and a scale showing the colours of the various rock formations, with a request that they will as far as possible fill in the blanks from the records of the departments in the respective colonies. By this means it is anticipated that much reliable information will be obtained, as