Dec. 29, 1887] 



NA TURE 



20; 



the choice of methods for the attack ^of each special 

 Problem. 



His Elementary Physics, and his Conservation of 

 Energy, are popular works on physics rather than scien- 

 tific treatises : — but his Treatise on Heat is one of the 

 best in any language, a thoroughly scientific work, spe- 

 cially characteristic of the bent of mind of its Author. 



Stewart published, in addition to his Kew Reports, a 

 very large number of scientific memoirs and short papers. 

 Many of these (notably the article in the Encyc. Brit., 

 9th edn.) deal with Terrestrial Magnetism, in itself as 

 well as in its relations to the Aurora and to solar disturb- 

 ances. A valuable series of papers, partly his own partly 

 written in conjunction with De la Rue and Loevvy, deals 

 with Solar Physics. His paper on the Occurrence of 

 Flitit Implements in the Drift {Phil. Mag. 1862, I.) seems 

 to have been ignored by the " advanced " geologists, one 

 of whose pet theories it tends to dethrone ; and to have 

 been noticed only by physicists, especially Sir W. Thom- 

 son, whose beautiful experiments have done so much to 

 confirm it. His paper on Internal Radiation in Uniaxal 

 Crystals, to which Stokes alone seems to have paid any 

 attention, shows what Stewart might have done in Mathe- 

 matical Physics, had he further developed the genuine 

 mathematical power which he exhibited while a student 

 of Ke Hand's. 



I made Stewart's acquaintance in 1861, when he was 

 the first-appointed Additional Examiner in Mathematics 

 in the University of Edinburgh, a post which he filled 

 with great distinction for five years. A number of 

 tentative investigations ultimately based upon our ideas 

 as to possible viscosity of the luminiferous medium, effect 

 of gravitation-potential on the physical properties of 

 »■ matter, &c., led to the publication of papers on Rotation 

 of a disc in vacuo. Observations with a rigid spectroscope, 

 Solar spots and planetary configurations, &c. These, as 

 well as our joint work called The Unseen Universe, have 

 been very differently estimated by different classes of 

 critics. Of course I cannot myself discuss their value. 

 There is, however, one of these speculations, so closely 

 connected with Stewart's Radiation work as to require 

 particular mention, especially as it seems not yet to have 

 received proper consideration, viz. Equilibrium of Tem- 

 perature in an enclosure cofitaining matter in visible 

 motion. (Nature, 1871 ; iv. 331.) The speculations 

 are all of a somewhat transcendental character, and 

 therefore very hard to reduce to forms in which they can 

 be experimentally tested ; but there can be no doubt that 

 Stewart had the full conviction that there is in them all 

 an underlying reality, the discovery of whose exact nature 

 would at once largely increase our knowledge. 



Of the man himself I cannot trust myself to speak. 

 What I could say will easily be divined by those who 

 knew him intimately ; and to those who did not know 

 him I am unwilling to speak in terms which, to them, 

 would certainly appear exaggerated. 



P. G. Tait. 



CHRISTMAS ISLAND. 



pROFESSOR NEWTON sends us the following 

 -*- extracts from a letter received by him from Mr. 

 J. J. Lister, M.A., St. John's College, Cambridge, the 

 naturalist on board H.M.S. Egeria, Commander Aldrich, 

 R.N., describing the recent visit to that little-known 

 island : — 



"We left Batavia on Tuesday, September 27, about 

 5 a.m., and were in the Straits of Sunda by the afternoon. 

 We saw the hills on the Java side clearly, scored by many 

 steep-sided valleys, and the green of the fields contrasting 

 brightly with the red volcanic earth. Behind these nearer 

 hills one of the great conical mountains loomed out every 

 now and then from his covering of clouds. To the west- 



ward, and more distant, a high volcanic peak on the main 

 island of Sumatra rose above nearer islands, and later in 

 the afternoon we saw the simple conical mass of Krakatab, 

 Next day we were bouncing about in deep blue water, as 

 we steamed south against a head-wind— a change after 

 the quiet sailing over the pale green shallow seas in which 

 we had been since we entered the Straits of Malacca. 

 On Friday, September 30, we reached Christmas Island. 

 The first we saw of it was a long line against the south- 

 east horizon, with a shallow saddle in the middle and a 

 gradual rise at either end— that to the west being the 

 higher. On nearer approach the island was seen to be 

 uniformly covered with trees, with a low cliff, much 

 undermined at the water's edge ; above this a gradual 

 slope leads to another steep ascent, which in some places, 

 especially at the projecting headlands, is a bare cliff, in 

 others covered with trees. From this there is a gradual 

 rise to the top. We found that there is a cap of coral 

 limestone over the whole island. The top is formed ©f 

 gray pinnacled masses with steep fissures between them, 

 and the surface of the rock is worn into a rough honey- 

 comb with sharp points and ridges which break under 

 foot and show the glistening white rock. On the slope ot 

 the island this rock forms horizontal terraces, with a rough 

 slope of pinnacled masses or a sheer cliff leading down 

 from them, and these seemed to be in a general way con- 

 tinuous at the same level along the side .of the island. I 

 suppose they mark the pauses in its gradual elevation 

 during which a fringing reef has formed. Some pieces of 

 rock, apparently volcanic, were picked up at Flying-fish 

 Cove, but it was not found where they had fallen from. 



"No stream or standing water was found. Apparently all 

 the rain that falls soaks into the porous rock at once. The 

 vegetation, however, looked fresh and green, and the under 

 parts of fallen logs were sodden with moisture. On two 

 of the nights during the ten days we were there, there 

 was heavy rain ; otherwise we had fine weather. Many 

 of the trees are tall, reaching 150 to 170 feet or more, and 

 some of them have vertical buttresses at the base, which 

 wind about horizontally and give off secondary buttresses. 

 They are often laden with great clumps of birds'-nest ferns, 

 as well as with other ferns, orchids, and parasitical trees, 

 and their trunks are festooned with long straight lianas. I 

 only found two orchids with flowers out, but these were 

 small and inconspicuous. Along the shore there are 

 tangled thickets of screw pines, and another kind grows 

 on the higher part. A large proportion of the trees bear 

 edible fruits. Altogether I am sending home some fifty 

 kinds of flowering plants and fifteen of ferns. 



" The rat {Mus macleari) swarms on the island. They 

 come out at dusk, and run about, in and out of the tents 

 that were pitched by the shore, through the night. There 

 is another kind of rat which is larger and black, except 

 where the scanty fur on the feet allows the pale skin to 

 show. There is also a shrew mouse, whose short shrill 

 squeak may often be heard in the woods. I caught three 

 of them one night in a pitfall. Several specimens of the 

 fruit-eating bat {Pteropus natalis) were obtained, includ- 

 ing males, which have no pale-coloured tippet, as Mr. 

 Thomas [P.Z.S., 1887, p. 512] thought might possibly be 

 the case. There is a small insectivorous bat in the 

 island, but I did not succeed in getting one. 



" The large fruit-eating pigeon {Carpophaga whartoni) 

 is very common. They congregate in the fruit-bearing 

 trees, and may then be shot by the dozen. They are 

 excellent eating, and supplied fresh meat for the ship. 



"There is a small dove — brown, with a rich bronzy-green 

 on the back and wings — which is very common. Their 

 habits are remarkably in keeping with their colouring. 

 On trees they are restless and seldom seen, but on the 

 ground, among fallen brown and green leaves, where 

 their colour makes them very inconspicuous, they seem 

 to have no fear. I shot seven one morning close to our 

 place : they were feeding in pairs on fallen berries, and 



