250 



NATURE 



[January 12, 1893 



fori a more searching and exact investigation of their 

 atomic masses, e.^. elements such as tellurium, which 

 occupies a position in the periodic system not in harmony 

 with its atomic mass, and cobalt, which plainly occupies 

 the intermediate position between iron and nickel, and 

 therefore should be intermediate in atomic mass. 



In a number of cases the accepted value is based on 

 the investigation of but a single interchange, the value 

 for iron, for instance, being practically based on the 

 results obtained on converting the metal into ferric oxide, 

 and vice-versa; and the relation of hydrogen to oxygen 

 having been established by the reduction of cupric 

 oxide. It is desirable that in such cases other and in- 

 dependent methods should be resorted to, eg. that 

 oxides of a number of metals other than copper should 

 be reduced, with the object of detecting possible constant 

 -errors. 



It is eminently desirable that an attempt be made to 

 directly determine the ratio of hydrogen to each of the 

 halogens without in any way bringing in the atomic mass 

 •of oxygen. Prof Mallet suggests various methods deserv- 

 ing of study. Also it is very important that the metals 

 of the yttrium and didymium groups should be further 

 investigated. Prof Mallet rightly terms the yttrium 

 group the opprobrium of inorganic chemistry. 



Nearly all that has been written hitherto in regard to 

 the periodic relationship among the elements has involved 

 the use of roughly approximate values only ; but it is time 

 that the foundation be laid for a more minute and critical 

 study of the periodic system of classification. Anomalies 

 in the classification as we now find it in our books, 

 glimpses of more detailed relations than as yet clearly 

 appear, tantalizing suggestiveness in so much of what 

 is already before us, call for more precise determinations 

 of the numbers we would discuss before we allow pre- 

 mature discussion to drift into mere fanciful speculation. 



In regard to the methods which it is desirable shall be 

 pursued in the determination of atomic masses. Prof. 

 Mallet has much to say. He discusses the selection of 

 processes, the purity of materials, the very numerous 

 directions in which vigilance must be exercised in order 

 to avoid extraneous or accidental causes of error, the 

 quantities of material to be used, the practical precautions 

 to be observed so as to secure accuracy of manipulation 

 and in weighing and measuring, the mode of stating 

 and calculating results, finally calling attention to the 

 advantage to be derived from the application of greater 

 working force and ampler means than can be commanded 

 by private individuals to the determination of atomic 

 masses ; with reference to this last point, during the 

 discussion on the paper, the opinion was freely expressed 

 that it was undesirable that such work should be carried 

 out in organized public or semi-public laboratories. 

 The question is, no doubt, a difficult one to settle — 

 such work demands a special temperament combined 

 with genius of a high order and an infinite capacity 

 for taking pains, qualities which must rarely occur 

 united in a single individual. Moreover, in order that 

 the value of a result may be appraised, it is essential to 

 overlook every detail involved in the determination. 

 Given the man, however, there can be no longer a doubt 

 that every possible assistance he may require should 

 be afforded him. It is marvellous that men like 

 Berzelius and Stas, working all but alone and unaided, 

 should have achieved results of such magnitude and 

 universal importance — the moral effect of their example 

 is certainly not less important than are the actual 

 results of their labour. 



The last section of Prof. Mallet's paper is devoted 

 to the discussion of the form in which it is desirable 

 ■finally to state the results. He here advocates the uni- 

 form substitution of the expression " atomic mass " for 

 "atomic weight," on the ground that precision in lan- 

 guage conduces to precision in thought — an aphorism 



NO. 121 I, VOL. 47] 



far too commonly disregarded by chemists. We have 

 now clear conceptions of atoms having constant mass 

 for the same element, of determinable difference of mass 

 in the case of different elements, the several masses and 

 numbers of which regulate the composition of all known 

 substances and the products resulting from interaction 

 among them. The atomic theory has advanced far 

 beyond the condition of a mere working hypothesis on 

 which chemists long stood with more or less uncertain 

 feet ; but even if this were not so, considering it, to use 

 a common metaphor, only as a scaffold, there is no good 

 reason, so long as we stand on it and work from it, that 

 we should be careless about tying our scaffold-poles and 

 nailing our planks. 



Lastly, Prof Mallet urges that all atomic masses shall 

 be expressed in terms of the mass of the hydrogen atom 

 taken as unity, objecting strongly to the change to 0=i6 

 which several writers have recently advocated, the most 

 objectionable argument put forward in favour of such 

 change being, he thinks, that the numbers we use are 

 expressive of ratios only — that any figures are allow- 

 able which correctly express combinmg ratios, and that 

 there are no reasons for using one set of figures rather 

 than another save mere arithmetical convenience. This 

 involves a grave error, as in adopting as unity the mass 

 of a single atom of any particular element, preferably 

 that one of which the mass is the smallest, we have 

 reason to believe that we express the mass of all the 

 others in terms of this as a really existent, definite, 

 and constant quantity of matter. It is, indeed, difficult 

 to understand when the scientific necessity in so many 

 cases of taking hydrogen as the unit is realized, how 

 the change to O = i6 can be advocated except on the 

 simple utilitarian plea that it is to the analyst's conveni- 

 ence. 



Prof. Mallet's monograph is undoubtedly a most ad- 

 mirable exposition of the philosophical lessons to be 

 learnt from the contemplation of Stas's labours. 



EXTINCT MONSTERS^ 



nPHE volume with this title treats of large animals. It 

 -■- is clearly and simply written, without any pretence 

 at being scientific, and is an excellent book for boys and 

 unlearned people who are curious to be informed upon the 

 subject of fossil animals. It would have escaped criticism 

 altogether but for emphatic words of praise in the preface, 

 and one or two passages in which the author, with second- 

 hand information, speaks authoritatively of predecessors 

 who restored extinct types of life with the slender materials 

 which were availible forty years ago. The attraction of 

 the volume and its novelty is a series of restorations of 

 saurians and mammals drawn chiefly by Mr. Smit. These 

 for the most part are based upon the restorations of 

 skeletons made by Prof. Marsh, whose discoveries have 

 inspired Mr. Smit's pencil as much as they have in- 

 fluenced the author's pen. There is not much anatomy 

 beneath the skins of the " Monsters," and they have an 

 aspect as though cotton-wool had taken the place of 

 muscle, or as though the drawings were models for the 

 " Lowther Arcade." This, however, is of less importance 

 than the answer given to the question. Are they reason- 

 ably faithful to nature? It does not seem to me that 

 they can claim this merit ; they are only reasonably 

 faithful to Marsh. Prof Marsh draws an animal so as 

 to give one type the maximum height to which the bones 

 can be hoiste 1 ; while another is given the maximum 

 length to which the remains can be extended. My own 

 studies would not have led me to reconstruct one of 

 the extinct reptiles upon the lines which are adopted in 



' "Extinct Moasters." A popular accouat of some of the larger forms of 



ancient animal life. By Rev. H. N. Hutchinson, B.A.., F. G S., with illus- 



i trations by J. Smit and others. (London : Chapman and Hall, Ld., 1892.) 



