Royal Institution. 309 



while all the rest of the class have only seven. Hitherto, this devia- 

 tion from the general plan has seemed to be without a motive j as it 

 appeared, that where length and flexibility were required, these quali- 

 ties were perfectly attained by lengthening each vertebra, without 

 adding to the number of them. The reason of the exception is now 

 pointed out. The sloth, in its inverted position, and confined in its 

 line of march to follow the branch on which it is placed, requires the 

 power of looking directly backwards. As a long neck would be an 

 incumbrance, it has received an additional number of short joints, 

 which enable it to turn its head within a short space. 



This remark appears to have been first made by Mr. Burchell, who 

 has observed these animals, with great facility, to twist their heads 

 quite round, and look in the face of a person standing directly be- 

 hind them. __ 



FRIDAY-EVENING PROCEEDINGS AT THE ROYAL INSTITUTION 

 OF GREAT BRITAIN. 



The evening meetings commenced on the 25th of January, when 

 Mr. Brande delivered a discourse on Chemical Notation. 



Mr. Brande stated that his objects in bringing the subject of che- 

 mical notation before the Members of the Royal Institution were two- 

 fold ; to inform the readers of foreign chemical works of the meaning 

 of the symbols generally adopted abroad, and to submit to the con- 

 sideration of English chemists, and especially of teachers ot chemistry, 

 a system of symbolic notation, more consistent with algebraic nota- 

 tion, and not open to the inconveniences and misconstructions which 

 the adoption of Berzelius's system would probably involve. He then 

 adverted generally to the great advantages that had been conferred 

 upon chemistry in its theoretical and practical relations, by the gra- 

 dual development of the atomic theory j and as all notation was a 

 mere concise statement and expression of the facts furnished by that 

 theory, he proceeded, in the first instance, to offer a few preliminary 

 remarks in illustration of its principles, taking for the purpose the 

 several chemical combinations presented to us by the union of the 

 elements of the atmosphere, nitrogen and oxygen, which, in the 

 immense ocean of aeriform matter that surrounds our planet, are in 

 a state of mechanical mixture, but which may be made to enter into 

 chemical union, and then give rise to no less than five definite pro- 

 ducts. Mr. Brande then exhibited the character of the separate 

 constituents of the atmosphere, and opposed them to the above com- 

 binations j namely, the nitrous oxide, the nitric oxide, the hyponi- 

 trous acid, the nitrous acid, and the nitric acid, and referred to a 

 table, showing the relative proportions per cent, of the nitrogen and 

 the oxygen in these several compounds. From this table it was ob- 

 vious that they exhibited a striking instance of the law of multiple 

 proportions ; for the numbers were such, that 14 parts (by weight) of 

 nitrogen, were shown successively to combine with 8, 16, 24,32, and 

 40 parts of oxygen, these latter numbers being to each other as 1,2, 

 3, 4, and 5 j accordingly, in the language of the atomic theory, one 

 atom of nitrogen was said to combine successively with one, two, 

 three, four, and five atoms of oxygen ; and we obtain the numbers 

 22, 30, 38, 46, and 54, as the equivalents or atomic weights of the 



