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previously published investigations into the theory of earthquakes" (p. 260). The reviewer may not have been able or not taken the trouble to distinguish the old from the new; but as a fact, the greater part of those forty-six pages is of matter never before published.

So also it is scarcely candid to object that "no reference is found to any of the Continental men of science who have done so much for terrestrial vulcanicity," which is contrary to the fact, for I have referred by name or by their labours to the few who have in any way advanced our knowledge as to the nature and origin of volcanic heat, without noticing that within that scope only was I by space obliged to confine myself, as stated in pp. 48, 49, 54, 76, &c.; the phenomena occurring at volcanic vents, which have chiefly engaged the attention of Continental and all other volcanic authors being avowedly outside my limits, and, I might add, but too often of secondary importance.

The nomenclature generally of my "Translation of Palmieri " is said to be objectionable, because such terms as sulphide of potass and terrochloride of ammonia are encountered. I have looked through the pages since without being able to discover these dreadful terms. However I am ready to take the reviewer's word that such a slip in proof correcting may be found in some place, and I humbly bow to such microscopic, profound, and valuable criticism, though, as stated, the conclusion is a good deal wider than its premises. ROBERT MALLET

Enmore, The Grove, S.W., March 5

Effect of Resistance in modifying Spectra IN a review of M. Guillemin's work "The Forces of Nature" which appeared in last week's Athenæum, the following reference, by M. Guillemin, to the experiments of M. Mitscherlich is quoted: "Suivant ce physicien il arrive que la presence de certaines substances dans une flame a pour effet d'empecher de se produire les spectres des autres substances, d'enteindre leurs raies principales." The English editor adds

A good example is given by "F. R. G. S.," in the last number of NATURE; the anecdote of his riding-horse, by Mr. Darwin, also seems to illustrate this point. In an article on the "Consciousness of Dogs," in the Quarterly Reviews, of last October, the following remarkable instance, amongst others, is mentioned on indisputable authority. A hound was sent by Charles Cobbe, Esq., from Newbridge, county Dublin, to Moynalty, county Meath, and thence, long afterwards, conveyed to Dublin. The hound broke loose in Dublin, and the same mom. ing made his way back to his old kennel at Newbridge, thos completing the third side of a triangle by a road he had never travelled in his life.

Now as Mr. Wallace's theory does not explain these and similar instances, it clearly cannot be received as a solution of the question. Moreover, not only does the faculty exist in other animals not remarkable for their sense of smell, but we find it in cases where this sense has nothing to do with it. Take, for example, the direct homeward flight of the carrier pigeon. Under the same head may be brought the migrations of birds and fishes, and the habits of the turtle, as mentioned by Mr. Darwin.

The writer in the Quarterly suggests a sense of the magnetic currents of the earth-a sort of internal mariner's compass in fact. But it is difficult to see how this could have helped the dog to find its way from Dublin to Newbridge, for instance, unless it was also able to consult a map so as to ascertain the relative position of the two places.

It seems then that the problem still remains unsolved. Either we must extend almost indefinitely the range of smell and sight; or, we must suppose the existence of some peculiar sense of the nature of which we are ignorant, which enables its possessor ta retain, as F. R. G. S. expresses it, "a constant perception of the bearing of its old home." Bath, March 17

POSSESSION ISLES

J. T.

that the effect "may probably be explained by the observations AS the idea of occupying Possession Islands as a

of Frankland and Lockyer."

In relation to this subject of the extinction of the bands of one metal by another, you will perhaps permit me to quote a paragraph from one of the lectures which I have recently had the honour of delivering in the United States. The arcs of thallium and silver had just been compared, and their similarity of colour pointed out. The power of prismatic analysis to show that, notwithstanding the apparent identity of colour, the arcs really belonged to two different metals, was then demonstrated. The metals were afterwards subjected together to the action of the Voltaic current, and it was shown that the band of thallium fell midway between the two bands of silver. Hence the similarity of colour. The lecture then proceeds thus :"But you observe here another interesting fact. The thallium band is at first far brighter than the silver bands; indeed the latter have wonderfully degenerated since the bit of thallium was put in. The reason of this is worth knowing. It is the resistance offered to the passage of the electric current from carbon to carbon that calls forth the heating power of the current. If the resistance were materially lessened, the heat would be materially lessened; and if all resistance were abolished there would be no heat at all. Now thallium is a much more fusible and vaporisable metal than silver, and its presence facilitates the passage of the current to such a degree as to render it almost incompetent to vaporise the more retractory silver. But the thallium is gradually consumed; its vapour diminishes, the resistance consequently rises, until finally the silver bands are rendered as bril

liant as at first."

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station for observing the Transit of Venus has been lately propounded, I have been requested to communicate to NATURE the results as to its climate, which we have obtained in this office from the logs of H.M.S. Erebus and Terror, which we are now re-discussing with a view to publication.

Possession Isles are in lat. 71° 56' S., long. 171° 7′ E H.M.S. Erebus and Terror were within lat. 70° to 721 S, and long. 170° to 175° E. from 10th to 17th January, 1841. During these eight days the mean height of the barometer was 29'143, mean temperature of the air 29° 7, and of the sea 30°5; the wind was variable, but chiefly from S. and SSW., force 6; the weather was clear ten times, cloudy twenty times, overcast eighteen times, from forty-eight double sets of four-hourly observations, while snow was noted nine times, and squally weather ten times.

The ships were within the same area on 20th and 21st February, 1841; and, during these two days, the mean height of the barometer was 28'920 inches, mean tempeSE., force 9 to 5; the weather was cloudy and overcast. rature of the air 23°5, of the sea 30°; wind WSW, to

Hooker, which he kindly sent me in reply to my inquiries In addition I am permitted to enclose a letter from Dr. as to his reminiscences of his visit to these inhospitable regions, and which he has allowed me to publish. Meteorological Office

ROBERT H. SCOTT

Letter from Dr. Hooker Possession Island, or rather Possession rock, is in a very inaccessible position. The chance of landing a wellequipped party upon it when reached, and the prospect of its subsequent removal by ships, if landed on, is very small. In any case I feel little uncertainty as to what would be the fate of a party left there for the winter, and the prospect of their seeing the transit would be abso lutely nil.

To reach it we "took the pack" January 3, 1841, and had not penetrated it till the 9th, aided at last by a furious gale. We then discovered South Victoria, and traced its coast from lat. 70° to lat. 78°, without finding a spot where it was possible to approach the shore. During the

twenty-two days that we spent off that continent, we never effected a landing but twice, and then, with the greatest difficulty, on two small volcanic islets, without a particle of vegetation on them, of which one was Possession Island (Jan. 13), a mere rock. The ship was hove to two miles off; with the greatest risk a landing was effected, on a beach of large loose stones and stranded masses of ice. It was no sooner done than the recall flag was hoisted in the ships, which were reached just as a terrific fog came on, followed by a gale of wind; ten minutes more and all hands in the boats would have been lost, for the currents ran like sluices between the land, islets, and icebergs. So much for Possession Island. (Read Ross's account of the landing, i. 188, and especially the paragraph at p. 190.)

Take a glance at the meteorological registers in Ross's voyage for the month of January 1841, which was passed between S. lat. 66° 32′ and 78°. The mean temperature was 29°02, max. 41°5, min. 19°5. It snowed on sixteen days; overcast, squally and misty was the usual weather, blue sky was rarely seen over more than a quarter of the heavens for a very few hours of the day, and for many days not seen at all.

66

In March between lat. 77° and 691°, the mean temperature was 24'28, max. 34°, min. 13. Sky as in January. In the following year our vessel went to the same seas. We took the pack" December 17, and after being all but wrecked, penetrated it after fifty-six days of great peril, and proceeded to 78° S., never once seeing land. During that January within 66° 32', and 67° 21' the mean temperature was 30°46, max. 40°5, min. 24°. It snowed on seventeen days, and we hardly ever saw blue sky.

In

In February between lat. 67° 18′ and 78° 12′, the mean temperature was 26°68, max. 35°, min. 165, and it snowed on twenty days. Blue sky was seen only on thirteen days. In 1842 the weather was worse than ever. that year we tried to get south in the meridian a little cast of Cape Horn, but never got beyond lat. 711, and then not till March 6th, having left the Falklands on the 18th December. In January of that year (1842) we were between lat. 63° 58′, and 64° 44′. The mean temperature was 30°9, max. 45°, min.23°5. It snowed on sixteen days -sky as before.

February-between lat. 61° 37′ and 66' or'. The mean temperature was 30'50, max. 35°5, min. 275. It snowed on twenty-four days out of the twenty-eight! Blue sky was seen only on seven days, and this on six days over one-eighth of the sky, and on the 7th over one-fourth.

With such a midsummer climate I leave you to guess the position of a party in lat. 72, cooped up through a winter on a rock a few yards long, covered with snow.

During the third year's cruise to the southward, Captain Crozier never once went to his cot, and we passed day and night with our hearts at the top of our throats.

The fact is, there is no summer or clear weather to be had, except by the rarest chance. For days and days we worked by Dead Reckoning alone. Storm, wind, and snow, are the prevalent summer phenomena. Still some seasons are not so bad as others, and Weddell got to 74 in an open sea in the meridian where we barely reached 66°. (Signed) J. D. HOOKER

Royal Gardens, Kew, March 6

The following is the account of the landing alluded to by Dr. Hooker:

"We found the shores of the mainland completely covered with ice projecting into the sea, and the heavy surf along its edge forbade any attempt to land upon it; a strong tide carried us rapidly along between this ice-bound coast and the islands amongst heavy masses of ice, so that our situation was, for some time most critical; for all the exertions our people could use were insufficient to stem the tide. But taking the advantage of a narrow opening that appeared in the ice, the boats were pushed through it, and we got into an eddy under the lee of the largest of the islands, and landed on a beach of large loose stones and stranded masses of ice. The island is composed

entirely of igneous rocks, and only accessible on its western side. We saw not the smallest appearance of vegetation, but inconceivable myriads of penguins completely and densely covered the whole surface of the island, along the ledges of the precipices, and even to the summits of the hills, attacking us vigorously as we waded through their ranks, which, together with their loud coarse notes, and the insupportable stench from the deep bed of guano, which had been forming for ages, made us glad to get away again, after having loaded our boats with geological specimens and penguins. Owing to the heavy surf on the beach, we could not tell whether the water was ebbing or flowing; but there was a strong tide running to the south, between Possession Island and the mainland, and the Terror had some difficulty to avoid being carried by it against the land-ice. Future navigators should therefore be on their guard in approaching the coast at this place.”

EARTHQUAKE WAVES

THE self-registering tide-gauges maintained by the the sea coast frequently exhibit, superimposed upon the United States Coast Survey at different points on tidal fluctuation, a succession of long waves, the origin of which is ascribed to distant earthquakes. In two notable instances, viz., the earthquake of Simoda in 1854, and that of Arica in 1868, the great ocean waves caused by the disturbance were distinctly registered in that way by the tide-gauges on the Pacific coast, and have been made use of for estimating the average depth along the lines of transmission. (See Coast Survey Reports for 1855, 1862, and 1869.)

Similar fluctuations were registered on the morning of November 17, 1872, shortly after local midnight, on the tide-gauge at North Haven, on the Fox Island, in Penobscot Bay, Maine. The fluctuations continued from midnight until nearly six o'clock in the morning, at somewhat irregular intervals of about seventeen minutes from crest to crest, with an average vertical range of nine inches, the greatest wave being at three o'clock, with a height of twenty inches.

No corresponding earthquake phenomena have come to the knowledge of the Coast Survey Office, and it is probable that if such was the case, the shock occurred somewhere under the Atlantic Ocean.

THE CHALLENGER EXPEDITION

H.M.S. Challenger cast off from the jetty at Portsmouth at 11.30 A.M. on December 21, with a low barometer. A strong south-westerly breeze was blowing, and the drum up; so that, especially in a season like the present, the prospect was not promising for the first few weeks of her voyage round the world.

The result justified the drum, and for a week we were knocking about the mouth of the Channel, and the Bay of Biscay, making slow progress southwards. It was perhaps as well to get a good shaking at first. It showed at once where there was a screw loose, and gave a chance to tighten it up. A sharp cyclone which caught the ship on her way from Sheerness to Portsmouth had already tested pretty fully the stowing of the apparatus, and although the Challenger rolls considerably when she is put to it (over 35°), not a single instrument shifted, and not a glass was broken, either in the zoological workroom, or in the chemical laboratory. Just before we got to Lisbon the weather improved a little, and we got some soundings and took one or two trial hauls with the dredge.

After leaving Lisbon on January 12 the wind was again fresh, but between Lisbon and Gibraltar we made some important experiments, and found, among other things, that we could work easily and successfully with the common trawl down to 600 fathoms. I am now writing about 100 miles north of Madeira, and since leaving Gibraltar the weather, though at first breezy, has been on

the whole fine. We have taken several successful navigative sounds at great depths, and we have trawled successfully at 2,125 fathoms, and recovered many interesting animal forms, several of them new to science, and others of extreme rarity and beauty. Still we must regard our work up to the present time as only tentative. The weather has been against us. It is altogether a new experiment to dredge from so large a ship, and it seems to present some special difficulties, or at all events to require some management. The weight of the ship is so great that there can be no "give and take" between it and the dredge, such as we have in the case of a smaller vessel. If there is any way on, the impulse to the dredge is irresistible, and seems to tend to jerk it off the ground. This difficulty can no doubt be met, but the only way of meeting it appears to be by using a length of rope greatly in excess of the depth-and having weights. A single dredging operation may thus occupy a great length of

time, but in compensation we have the greater size and efficiency of this dredge. The few trials which we have already made have been all in the direction of improvement, and I have little doubt that under Captain Nares' skilful management what little difficulty is still felt will shortly disappear.

As I hope to contribute to NATURE from time to time a series of articles giving the results of our voyage, it may be well to commence by giving a sketch of the general scope of our operations, and the means and appliances at our disposal.

The Challenger is a spare-decked corvette of 2,000 tons displacement. This particular build gives her an immense advantage for her present purposes, as she has all the accommodation of a frigate, with the handiness and draught of water of a corvette. Sixteen of the eighteen 68-pounders which form the armament of the Challenger have been removed, and the main-deck is almost entirely set aside

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for the scientific work. The after-cabin is divided into two by a bulk-head, and the two little rooms thus formed-still gay with mirrors, and pictures, and new chintz, and bright with home faces-are allotted to Captain Nares and myself. The fore cabin, a handsome room, 30 ft. long by about 12 ft. wide, into which these private cabins open, the captain and I use as a sitting room, the port-end with its writing-table and work-table, and its book-cases packed with old home favourites, being appropriated to my use and that of my secretary Mr. Wild; while the captain has arrangements at the starboard end of the same kind. Two sets of cabins have been specially built on the after-part of the main-deck for this difficult part of the scientific work. On the port side a commodious zoological work-room is occupied by the naturalist of the civilian staff, while the chart room corresponds with it on the opposite side. Towards the middle of the main-deck on the port side

there is a dark room and a working room, for the photographer, and on the starboard side Mr. Buchanan has his chemical and physical laboratory.

Nearly the whole of the fore-part of the main deck is occupied by the dredging and sounding gear, Mr. Siemens's photometric and thermometric apparatus, and the more cumbrous of our machines, such as the hydraulic pump, the aquarium, and other very valuable articles, of which a detailed description will be given hereafter.

I feel justified in going even so far as to say that the arrangements for scientific work in the Challenger leave little or nothing to be wished for. Captain Nares and his officers not only do everything which care and skill can accomplish to further our objects, but, having naturally a certain advantage over the civilians in rough weather, they keep us up to the mark by the lively interest which they take in the success of our operations. There is a common mess in a large ward-room on the lower deck,

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After this first attempt we tried the trawl several times at depths of 1,090, 1,525, and finally 2,125 fathoms, and always with success.

Several fishes, most of them allied to Macrourus, were added to the list. Several decomposed crustaceans, and among the lower crustaceans at 1,090 fathoms, a gigantic amphipod, of the family Hyperina, allied to Phronima. The eyes of this creature are very remarkable, extending in two great facettio lobes over the whole of the anterior part of the cephalo thorax, like the eyes of Aeglina among Trilobites. This crustacean, which is three and a half inches in length, makes a splendid drawing, and reminds one of the old Eurypterids, is in process of description at the hands of Dr. von Willemoes Suhm.

Mollusca are very scarce in deep water, and our catches have hitherto been chiefly confined to such things as the species of Nucula, Leaa, Verticordia, &c., familiar through the deep dredgings of the Porcupine. Among the molluscoids a haul in 1,525 fathoms gave us a lovely thing, a bryozoan. forming, out of branches closely resembling those of Accromarchis neritina, a graceful cup, the bases of the branches united by a transparent stem between two and three inches high, like the barrel of a quill, or the stem of a claret glass. This genus, which presents a general character totally different from any. thing hitherto known among recent Bryozoa, I men to dedicate to Captain Nares, as an early recognition of the confidence and esteem which he has already fully gained from the scientific staff. Naresia cyathus certainly recalls, in a most singular way, the Cambrian Dictyonema, a form which I had, however, hitherto been inclined to refer to the Hydrozoa.

The Echinoderms have yielded some exceedingly interesting species to the trawl; among them several examples of the beautiful little urchins, of which one specimen was taken by Count Pourtales, in the Straits of Florida, and described by Alexander Agassiz under the name of Salenia varispina. It is undoubtedly a true Salenia, and to an advocate of the doctrine of the "continuity of the chalk," it is pleasant to see in the flesh this little beauty, which has hitherto been reckoned among the lost

tribes.

Among the star-fishes two species of the genus Hymenastes have occurred, and the ophiurids are well represented chiefly by large examples of several species of the genus Ophiomusium.

All the hauls of the trawl, down to 2,125 fathoms, have yielded many specimens of a singular Holothurid, of which a description will shortly be published by Mr. Moseley. The animal is of a rich violet colour. Like Psolus, it has a distinct ambulating surface, with a central double line of water feet. The body cavity is small, but the perisom is represented by an enormously thick layer of jelly, which riscs on either side of the middle line of the back into a series of rounded lobes, each perforated for the passage of an ambulacral tube and corresponding therefore with an ambulacral foot. The upper pair of vessels of the trivium send out series of leaf-like sacs, richly loaded with pigment, which fringe on either side the ambulatory disc, and appear to be chiefly concerned in the function of respiration.

Sea-peas and Gorgonia have occurred frequently, always remarkable for their brilliant phosphorescence. Captain Maclear is giving special attention to this beautiful phenomenon. A Mopsea, which shone very brilliantly, gave a spectrum extending from the green well on into the red, while Umbellularia gave a very restricted spectrum sharply included between the lines b and D of this wonderfully rare sea-pea. We took with the trawl a very fine specimen, with a stem 3 ft. long, at a depth of 2,115 fathoms off Cape St. Vincent.

As usual in deep-sea work sponges preponderated, and the order has added several novelties, chiefly referable to the ventriculite group, the Hexactinellida.

Some fine new species of Aphrocallistes came up along the coast of Portugal, and off t. Vincent; with many spicules and more or less mutilated examples of Hyalonema, two or three species in fair condition of a species of Euplectella, with spicules which I cannot distinguish from those of Euphalelles aspergillum — the Venus flower-basket of the Philippines. The form of the two sponges is the same, but our own specimens are quite soft, the spicules not fused into a continuous siliceous network.

The physical and chemical observations will be fully detailed hereafter. The temperatures off the Coast of Portugal corresponded very closely with those taken in the Porcupine in 1870, and the Shearwater in 1871, below the first 100 fathoms through which at this season the temperature is nearly uniform. WYVILLE THOMSON

PROF. FLOWER'S HUNTERIAN LECTURES LECTURES X. XI. XII.

THE

HE fossil Dasypodide, or their existing allies, are found in America only. They may be divided into two classes, those closely resembling existing species, and those differing considerably from them. Most of the former have only been obtained in a fragmentary state; they have been studied by Lund; one was peculiar in having the teeth compressed from before backwards, instead of laterally. The latter class includes a wellknown form, Glyptodon, of which there are several species and perhaps more than one genus. An exhaustive monograph is in course of publication by Burmeister on the genus, and the material he has at his command at Buenos Ayres is very large. In 1839 Prof. Owen was among the first to describe it, he did so from the specimen now in the Museum of the College, giving it the name by which we know it. The Danish naturalist, Dr. Lund, at about the same time gave the name Hoplophorus to the remains of a very similar animal, and Burmeister considers that there is sufficient difference between the two type specimens of these authors, that of the latter having one less hind toe, to justify the generic name proposed by each being retained. In Glyptodon the carapace is proportionately thicker and stronger than in existing Armadillos; it is composed of distinct pieces in contact at their edges, but not anchylosed, except in aged individuals; it is never hinged transversely, so the animal could not roll itself up. A horny epidermis undoubtedly covered the shield, and hairs may have been present, as foramina are frequently found. The scutes vary in shape in different species, and are of different sizes in different parts of the same individual. The tail formed a thick cylindrical scute-covered column, which in some cases was armed with spines and swollen near the tips, like a giant's club. An approach to this peculiar shape is seen in the existing Chlamyaophorus. All known species have eight molars above, and the same number below on each side of each jaw, in a long straight, nearly parallel series, running very far back. The teeth all grew from persistent pulps, and were therefore long and slightly arched, with two deep flutings on each side, whence the name. In structure they were much as in the Armadillos, and the presence of the grooves caused the central harder osteodentine to assume a somewhat gridiron shape, which was sometimes much elaborated. The front of the skull was much truncated, and a strong ossified septum was often present. Burmeister thinks that the animal possessed a trunk. The brain was proportionately very small, the olfactory lobes and cerebellum preponderating. Much of the skull was occupied by air cells and the molar roots. The descending zygomatic process was very large, to give origin to the masseter muscle; it is absent or nearly so in the Armadillos; it may differ in character from that of the Megatherium, probably arising from the maxillaries, as it was

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