ride of potassium; the proportion between which gives the ratio which the respective equivalent numbers of each bear to one another, and also to that of chlorate of potassa. The equivalent of nitrate of potassa is next obtained by converting the chlorate and the chloride of potassium into that salt ; and from these data the equivalents of chlorine and of nitrogen are deduced. A similar train of inquiry is next instituted with the corresponding salts having sodium for their base : chlorate of soda being decomposed into the chloride, and into the nitrate ; nitrate of soda into chloride ; and chloride of so- dium into nitrate of soda. The results of these different series of experiments coincide so closely with one another as mutually to con- firm their general accuracy in the most satisfactory manner. For the purpose of determining the equivalent numbers of the element- ary bodies themselves, (namely, chlorine, nitrogen, potassium, and sodium,) the author employed the intermedium of silver, the several saline combinations of which with chlorine and with nitric acid w^ere found to afford peculiar advantages for the accurate determination of the relative weights of the constituents of these salts, when subjected to various combinations and decompositions. The conclusions to which the author arrives with regard to the equivalent numbers for the six elementary bodies in question, tend to corroborate the views of the late Dr. Turner, and to overturn the favourite hypothesis that all equivalent numbers are simple multiples of that for hydrogen. He finds these numbers to be as follow :
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Oxygen 8'
Chlorine 35-45
Nitrogen 14*02
Potassium 39 '08
Sodium 23-05
SHver 107*97
The author~intends to pursue these inquiries, by applying similar methods to the investigation of other classes of salts.
January 31, 1839.
JOHN W. LUBBOCK, Esq., Vice-President and Treas., in the Chair.
John Wesley Williams, and James Yates, Esqrs., were severally elected Fellows of the Society.
A paper was read, entitled, " Some account of the Art of Photo- genic Drawing, or the Process by which Natural Objects may be made to delineate themselves without the aid of the Artist's Pencil." By H. F. Talbot, Esq., F.R.S.
In this communication the author states, that during the last four or five years he has invented and brought to a considerable degree
