Apru 2 2, 1875] 



NATURE 



485 



The heat produced by the passage of the spark through 

 the strip of tinfoil is suiScient to expand the air in the 

 bottle again, and the drop of water is pushed outwards by 

 the expanding air through a space of one or several 

 millimetres." 



Fig. 6 is a simple form of the so-called "injector" or steam- 

 jet pipe for feeding the boilers of steam-engines. A glass 

 tube, a a, has corks fitted at each end into which pass the 

 tubes cc d. Steam issues from the small aperture in b, and 

 expanding passes out into the air through c. The air 

 within a a becomes rarefied, and the water into which the 

 tube d dips is thus driven by atmospheric pressure into, 

 and finally ejected from, c. 



" The construction of the little injector presents no 

 difficulty, but the dimensions of the various parts must be 

 exactly those shown inthe figure, if the action is to be 

 depended upon. Each side of the right angle into 

 which the jet tube is to be bent should be about 3 cm. 

 long, and the tube as wide as c ; the pointed end should 

 be like that of b, or very little narrower. An india-rubber 

 suction-tube, 10 or 15 cm. long, may be attached to d. 

 The india-rubber tube employed for connecting the 

 apparatus with the vessel in which the steam is generated 

 should fit very tight ; it must not be tied with thread, so 

 that in case the pressure of the steam becomes too great, 

 the india-rubber may be forced off the glass tube, instead 

 of its being torn or the glass broken by the pressure." 



Before closing the volume, we notice one or two places, 

 besides those previously alluded to, in which a little im- 

 provement might be made. For example, in describing 

 the construction of the gold-leaf electroscope, the mode 

 of cutting gold leaf is omitted. The author recommends 

 students " to have the strips cut and fixed to the flat end 

 of a wire by a skilled mechanician." This is unsatisfac- 

 tory, for students cannot have recourse to a skilled work- 

 man when they like. Nor is there any very great diffi- 

 culty about cutting and fixing the gold leaves when the 

 proper method is patiently tried. Here, as throughout all 

 practical work in physics, perseverance is the essence of 

 success. Again, we observe that useful little instrument 

 the " carrier," or proof-plane, might be more readily made 

 than is stated here. The simplest plan is to procure an 

 ebonite penholder, and fasten a disc of gilt paper at the 

 end intended for the pen. These penholders are most 

 useful adjuncts to a physical laboratoiy. 



Further on, radiant heat receives rather meagre treat- 

 ment. There is no description of any form of air-thermo- 

 meter, an instrument which in a modified shape is capable 

 of doing most useful work through the whole subject of 

 heat. Nor is the subject of magnetism so fully treated as 

 we should have expected ; and in current electricity some 

 description should have been given of the measurements 

 of resistance and electromotive force : a simple form of 

 Wheatstone's bridge — such, for example, as that sug- 

 gested by Prof. Foster — can readily be made, and is in- 

 dispensable for the proper study of this subject. 



But the work is intended e.s an introduction to the 

 study of physics, and, as such, it is altogether the best we 

 have yet met with among English hand-books. The 

 volume unfortunately is of an unwieldy size, and might 

 have been made far more convenient for the constant 

 reference it requires if a better arrangement of type had 

 been adopted. W. F. B. 



DRESSER'S "BIRDS OF EUROPE" 

 A History of the Birds of Europe, including all the 

 Species inhabiting the Western Palaarctic Rej;ion. By 

 H. E. Dresser, F.Z.S., cS:c. (Published by the Author, 

 by special permission, at the Office of the Zoological 

 Society of London.) 



THE issue of Parts 35 and 36, completing the third 

 volume, affords us the occasion of again noticing 

 the progress of this beautiful and important work. 



The energy with which the author has laboured to 

 ensure punctuality in the issue is beyond all praise ; and 

 now that about half the work is completed, and we find 

 that the last twelve parts, with figures of nearly 120 

 species of birds, have appeared within the year, sub- 

 scribers have every assurance that they will, in due course, 

 possess a finished work. 



And this punctuality of issue is not effected by any 

 haste or carelessness of workmanship either in the plates 

 or the letterpress. In the last double number we find 

 some pictures which are -triumphs of artistic skill. Such 

 in particular is the figure of the Night-jar {Capiiniul^Jits 

 europaus), in which the downy softness of the plumage, 

 the exquisite mottling of the feathers, the roundness and 

 repose of the whole bird, the half-closed sleepy eye, and 

 the well-contrasted background, are exquisitely rendered. 

 The Wryneck ( Yunx torquitla) is almost equally good, 

 and the tail of this bird in particular is rendered with a 

 delicacy and skill which cannot be surpassed. Another 

 charming picture is that of the Smew {Mergus albellus), 

 surrounded by half a dozen young, whose various attitudes 

 and the grouping of the whole, with the quiet river scene, 

 are in admirable taste. The two Sand-martins [Cotyle 

 riparia) perched on bending reeds form another beautiful 

 bit of nature. An important feature of this work is the 

 care taken to figure the birds in all their different states 

 of plumage, and more especially that of the young or 

 nestling birds. In this part we have four species in 

 which the young are figured — the Black-winged Kite, 

 the Pied Flycatcher, the Dottrell, and the Smew — and in 

 every case the plumage of these infants is remarkably differ- 

 ent from that of their parents. The introduction of these 

 young birds adds greatly to the variety and interest of the 

 plates as mere pictures ; but they also have a high scientific 

 value, since they are with good reason believed to indicate 

 what was probably the plumage of the ancestral form of 

 the group to which they belong. From this point of 

 view, the young are really very old birds indeed, and 

 may, when thoroughly studied, enable future ornitholo- 

 gists not only to reconstruct the forms, but also to repro- 

 duce the colouring of the birds of past ages. They thus, 

 to some extent, make up for the deficiency of fossil 

 remains of birds ; and this work, when completed and 

 the plates arranged in systematic order, will be invaluable 

 to the philosophic naturalist. 



It is difficult to choose an extract which shall give any 

 adequate idea of the valuable scientific matter to be found 

 in the letterpress. The following passage (somewhat 

 condensed), taken from the account of the Night-jar, 

 touches on a difficult question which the observations of 

 some of the readers of NATtjRE may help to clear up : — 



" The Night-jar feeds on moths, beetles, and insects of 

 various kinds, most frequently capturing its prey on the 

 wing, its capacious gape forming an excellent moth or 



