Aug. 12, 1875I 



NA TURE 



289 



real use to the student. We are told that a millifram of hy- 

 drogen contains' about 400,000000,000000,000000 atoms of 

 hydrogen, and a milligram of gold 2,000000,000000,000000 

 atoms, while the atomic weight of gold is given as 196 ; 

 if this is admitted, the milligram of gold will contain 

 some 408 1 6,000000,000000' atoms in excess of the number 

 given above, and the omission of this will in itself show 

 the extreme generality of such statements. A curious 

 deduction as to ^tform of atoms is drawn from the fact 

 that many minerals are observed, when reduced to pow- 

 der, to preserve their normal crystalline form ; hence, 

 says our author, " we conclude the compound atom 

 possesses form closely related to the cleavage form." 



The law of Dulong and Petit is very concisely stated, 

 and its importance in modem chemistry is well illus- 

 trated. It is crudely formulated thus : — if a represents 

 the atomic weight and s the specific heat, the product 

 a s will be the specific heat 6" of a gram-atom of the sub- 

 stance, and S = as nearly equal to 6*3. 



Or again, if the specific heat 6" of an element be known, 

 an approximate determination of the atomic weight can 

 be found as follows : — 



a — nearly -^ 

 s 



Thus the specific heat of lead = o'03i, consequently 



,-— - = 200, the exact atomic weight of lead being 207. 



The service afforded by the application of this law to the 

 determination of the right atomic weight of an element 

 is also shown in this case of lead, for from the analysis 

 of oxide of lead the atomic weight of lead might be 207, 

 or 103.5, or 69, or 414, or 621, for although we find 

 that sixteen parts by weight of oxygen are united with 

 207 of lead, we have no direct chemical proof that the 

 207 represents one atom ; but the law of Dulong and 

 Petit now steps in and shows us that the right atomic 

 weight is 207, because it alone satisfies the conditions of 

 that law. And so for other elements the vapour density 

 of whose compounds cannot be determined. The section 

 on Atomicity or valence would be much improved by the 

 introduction of a complete list of the elements with their 

 atomicities, and a discussion of doubtful atomicities. 



In the seventh section the author passes at once from 

 what were once called inorganic compounds to the discus- 

 sion of organic substitutions as shown in the great methyl 

 series of compounds. Such comprehensive statements 

 as, " the binary marsh gas,'also called methane^ CH^, is tho 

 basis of all organic compounds," are of great use to the 

 student, and in this instance the statement at once justifies 

 the passage from mineral chemistry to so-called organic 

 chemistry without one word of introduction or comment. 

 We do not think that the attempted graphical representa- 

 tion of chemical constitution in the eighth section can be 

 productive of anything but confusion^to the. student. The 

 crosses and dots and three-limbed signs have themselves 

 to be remembered, and cannot give any.precise idea of the 

 constitution of a complex compound. A somewhat detailed 

 account of the constitution and syntheses of various serial 

 compounds concludes that portion of the work devoted to 

 Molecular Statics. 



The second part commences with an account of the 

 motions of molecules, and it is asserted that since mole- 

 cules are not spherical, their impact against each other 



will not alone produce motion of translation, but also 

 motion of rotation, and this is partially illustrated by the 

 motion of a boomerang. The following definitions are 

 stated on the authority of the author : — 



1. " The molecules of a body in the gaseous condition 

 have a motion of translation, and also a motion of rota- 

 tion around their natural axis of maximum moment of 

 inertia." 



2. " The molecules of a body when in the' solid state 

 have only a vibratory motion about a position of equi- 

 librium." 



3. " The molecules of a body when in the liquid state 

 have a vibratory motion, as in the solid state, and also a 

 motion of rotation around their natural axis of minimum 

 moment of inertia." 



Among the concluding sections of the book is a very 

 interesting and suggestive account of caloraiioti, that is 

 the amount of heat produced or absorbed in any chemical 

 process. The treatment (p. 153), from a caloration point 

 of view, of the reactions of hydrogen, chlorine, iodine, 

 and silver, is worthy of careful study. A few pages at the 

 end ot the book treat of Systematic Chemistry and. 

 Applied Chemistry. 



Dr. Hinrich's book must be used in connection with his 

 former works, " Elements of Chemistry " and " Elements 

 of Physics," to which frequent references are made. It is 

 mainly intended ar, a guide to the student, and must be 

 used with the assistance of a teacher. To the advanced 

 student it will be found to be of great use, and most emi- 

 nently suggestive ; but it will be almost useless to any 

 reader who has not before acquired the main principles of 

 chemical science, together with a large storehouse of 

 chemical facts. The work is somewhat disfigured by 

 numerous misprints — dissociotio7i (p. 21), amides (p. 73), 

 reductian (p. 109), enery (p. 113), &c., and we think the 

 two plates at the end are extremely confusing ; but these 

 minor matters are easily remedied in a second edition, 

 and need not detract greatly from the value of a really 

 useful and comprehensive work. 



G. F. RODWELL 



THE ZOOLOGY OF THE ''EREBUS" AND 

 « TERROR." 



The Zoology of the Voyage of H.M.S. " Erebus " and 

 " Terror" under the command of Captain Sir James 

 Clark Ross, R.N., F.R.S., during the years 1839 to 

 1843. By authority of the- Lords Commissioners of 

 the Admiralty. Edited by John Richardson, M.D., 

 F.R.S., &c., and John Edward Gray, Esq., Ph.D. 

 F.R.S., &c. 



No. XIX. — Insects , (conclusion). By Arthur Gardiner 

 Butler, F.L.S., F.Z.S., &c. 1874. 



No. XX.— Crustacea. By Edward J. Miers. 1874. 



No. XXl.—Mollusca. By Edgar A. Smith, F.Z.S., &c. 



No. XXII. — Birds (conclusion). By R. Bowdler Sharpe, 

 F.L.S., F.Z.S., &c. 1875. 



No. XXIU.— Mammalia (conclusion). By John Edward 

 Gray, Ph.D., F.R.S., F.L.S., &c. 1875. 



No. XXIY.— Reptiles (conclusion). By Albert" Giinther, 

 M.A., M.D., Ph.D., F.R.S., V.P.Z.S. 1875. 



THE non-completion of the " Zoology of the Voyage 

 of the Erebus and Terror" has long been a 

 public scandal. The celebrated voyage of these ships, 



