298 Mr Clark on the PyropJiosphate of Soda, 



the distant waters of Lake Ontario, in North America, were 

 violently agitated at the time." — " The connection which earth- 

 quakes (continues Bakewell) have with distant volcanos, and 

 their frequency at particular periods, are truly remarkable. 

 The tremendous earthquakes in 1812 in the Carraccas were 

 followed by an eruption in the Island of St Vincents, from a 

 volcano that had not been burning since 1718, and violent os- 

 cillations of the ground were felt, both in the islands and on 

 the coast of America." 



The late swell of Lake Erie has been followed by shocks of 

 earthquakes, as well at a distance as in the vicinity. Have we 

 not, therefore, reason to believe, that the extraordinary agita- 

 tions which sometimes occur in the lakes are connected with 

 earthquakes, and produced by the same causes ? 



Art. XVII. — On the Pyrophosphate of Soda, one of a new 

 class of Salts produced hy the Actioti of Heat on the Phos- 

 phates. By Mr Thomas Clark, Lecturer on Chemistry 

 and Mechanics in the Glasgow Mechanics' Institution. 

 Communicated by the Author. 



The phosphate of silver is, according to Doctors Thomson 

 and Berzelius, an insoluble yellow salt, which is produced 

 when watery solutions of phosphate of soda and of nitrate of 

 silver are mixed. These eminent chemists, it is well known, 

 differ much as to the constitution of the phosphates in gene- 

 ral ; but in the instance of the yellow phosphate of silver, 

 they have each given analyses, which substantially agree. It 

 occurred to me, therefore, that by ascertaining the proportions 

 of the salts necessary for mutual decomposition, and of the 

 precipitate produced, and by adding a few collateral experi- 

 ments, it would be possible to decide the matter at controver- 

 sy, by starting from a point, at which both parties were agreed. 

 Having in this view commenced a set of experiments, I 

 soon came to an unexpected appearance, and found myself 

 engaged in a new train of research, the result of which I con- 

 ceive of sufficient importance to be laid before chemists with- 

 out delay. 



