442 APPENDIX. 



tact. Without this the battery could not ope- 

 rate. The figure represents Groves' battery, 

 with the thumb screws by which the wires 

 are connected with the platinum and zinc. 

 The outer dark portion within the cup is the 

 zinc, divided from top to bottom, that the acid 

 may flow freely, and come into contact with 

 both sides. 



307. 



THE ATOMIC THEORY. That combination takes place in 

 definite and multiple proportions, is directly proved by exper- 

 iment. Oxygen, for example, unites with hydrogen in the 

 proportion of 8, 16, 32 and 40, to one of the latter element, 

 and refuses to combine in any other proportion. If matter 

 were infinitely divisible, no reason can be assigned for this 

 fact. Each infinitesimal portion of oxygen possessing the 

 same affinities, we should expect to find combination in exact 

 proportion to the quantity supplied. 



Dalton's atomic theory, the truth of which is assumed in the 

 text, affords a luminous explanation of the facts under consid- 

 eration. According to this theory, oxygen combines with hy- 

 drogen in no smaller proportion than that of 8 to 1, because 

 this is the ratio of weight in the least existent particles of the 

 two substances. It combines in the proportion of 16, 24, 32 

 and 40, by uniting 2, 3, 4 or 5 of its atoms to one of Hydro- 

 gen. It refuses to combine in any intermediate ratio, be- 

 cause its atoms are indivisible. The same view of the con- 

 stitution of matter is essential to the explanation of innumer- 

 able facts in organic chemistry. 



The value of a table of atomic weights does not depend in 

 the least degree upon the reception of the atomic theory. 

 It is a list of combining proportions, determined by careful 



