THE SCIKNTIFIC NAME OE THE FLORIDA VELVET BEAN. 105 



Destructive criticism is a thankless and often useless task, 

 especially where one has not access to the materials for a recon- 

 struction of that which is criticised. But it seems necessary at 

 this time to issue a warning against adopting new names for old 

 crops, without sufficient reason. 



In other respects Miss Bort's publication is worthy of commen- 

 dation ; the plates are excellent, and the text shows a considerable 

 amount of patient research through ancient archives dealing with 

 the introduction into America of agricultural crops ; we wish that 

 inore of this might be done before all the old documents are 

 irretrievably lost, as has been the case, recently, with some of them. 



ATOMIC WEIGHT OF CARBON.— Last June Dr. Alexander 

 Scott, F.R.S., Director of the Davy-Faraday Research Laboratory, 

 announced, at a meeting of the Chemical Society, that, as a very 

 •concordant result of a number of preliminary determinations of 

 the amount of silver nitrate needed for the titration, according to 

 the method of Stas, of weighed quantities of pure ammonium 

 bromide, tetramethylammonium bromide, and tetraethylam- 

 monium bromide, he had arrived at the conclusion that the atomic 

 weight of carbon, instead of the present accepted value of 12.002 

 — the result, principally, of jihysical determinations — should be 

 -considered as 12.026. At the time these figures were challenged 

 by Dr. (now Sir Edward) Thorpe, then Director of the Government 

 Laboratories, and by Prof. Clarke, the English and American 

 representatives on the International Conmiission on Atomic 

 Weights, who at once objected to Dr. Scott's emplovment. in his 

 calculations, of what they regarded as an obsolete atomic weight 

 for silver (io7*93), while Sir William Ramsay and Prof. H. B. 

 Dixon, amongst others, enquired wliether precautions had been 

 taken thoroughly to dry the crystals of the salts titrated. Dr. 

 Scott disposed of the former objection by pointing out that the 

 atomic weight of silver, being eliminated in the course of his calcu- 

 lations, did not affect the final result, and stated, in reply to the 

 other enquiry, that the salts had been purified by sublimation. 

 At the Society's meeting on the 2nd December the subject was re- 

 verted to. Sir Edward Thorpe drew attention to a recent paper 

 by Guye and Zachariades {Coinptes Rendus, cxlix, 503). wherein 

 it is stated that the method ordinarily adopted for converting 

 weights of fine light powders to a vacuum standard gives incorrect 

 results owing to the occlusion of air, which may affect materially 

 determinations of the value of an atomic weight. To this possi- 

 bility Sir Edward ascribed the high atomic weight obtained by Dr. 

 Scott in his experiments. Sir Edward had worked out a calcula- 

 tion for error due to occluded air, and this almost exactlv accounted 

 for the higher value deduced by Dr. Scott. The latter value had 

 been considered by the International Committee on Atomic \'\'eights, 

 but was not accepted. Dr. Scott, in a replying paper, disputed the 

 accuracy of Guye and Zachariades' conclusions, and, taking Potas- 

 sium chloride, one of the salts quoted by them, pointed out that 



