466 Scientific Intelligence. [Dec. 



brilliant light emitted from charcoal, when submitted to galvanic 

 action, not only speedily affected the muriate of silver, but 

 readily caused the above gaseous mixture to unite, sometimes 

 silently, and often with explosion. The concentrated light of 

 the moon, like that from the gases, did not affect either of these 

 tests. The author in conclusion remarked, that having found 

 the photometer of Mr. Leslie ineffectual in these experiments, he 

 employed one filled with the vapour of ether (renewable from a 

 column of that fluid), and which he found more delicate. 



At this meeting, a paper, by Dr. Carson, was begun, " On the 

 Elasticity of the Lungs," 



Article XI. 



SCIENTIFIC INTELLIGENCE, AND NOTICES OF SUBJECTS 

 CONNECTED WITH SCIENCE. 



I. Arsenic. 



Arsenic is one of the simple bodies which has not yet been 

 reconciled in a satisfactory manner to the atomic theory. In 

 the last edition of my System of Chemistry, I deduced the 

 weight of an atom of it, from the best experiments hitherto made 

 on the subject, to be 4-75. I concluded likewise that the 

 oxygen in arsenious and arsenic acids were to each other as the 

 numbers 3 to 5, and that their constituents were as follows : 



Arsenious acid. .. 100 arsenic + 31-600 oxygen 

 Arsenic acid 100 +52-631 



This makes the numbers representing the atoms of arsenic and 

 oxygen united in these bodies as follows : 



Arsenious acid . .... 4-75 arsenic + 1-5 oxygen 

 Arsenic acid 4*75 + 2'5 



. or the first is a compound of 1 atom arsenic + 1-5 atom oxygen, 

 and the second of 1 atom arsenic -f 2'5 atoms .oxygen. It is 

 obviously possible to get rid of these fractional parts of atoms 

 by multiplying the preceding numbers by 2. This will give us 

 9-5 for the weight of an atom of arsenic, and arsenious acid will 

 be composed of 9*5 arsenic + 3 oxygen, and arsenic acid of 

 9-5 arsenic + 5 oxygen. An atom ot arsenious acid will weigh 

 12 5, and an atom of arsenic acid 14*5. I thought it premature 

 to propose this view of the subject till further experiment* 

 should be made on the composition of arsenious acid. 



Berzelius has since published a new set of experiments to 

 determine the composition of both these acids, and the propor- 

 tions in- which they unite with bases. These experiments I 



