118 Mr Ritchie on an extremely Cheap and 



ried off by the carbonic acid, the decomposition of the hydro- 

 sulphate will at last be complete. 



It is necessary to observe that these decompositions re- 

 quire a much greater quantity of acid than is sufficient to sa- 

 turate the base ; for the acid, separated from the base, can 

 only be removed from the solution by means of a great ex- 

 cess of the acid which takes its place, according to the theory 

 of vapours. 



It should also be remarked that, if the carbonate and 

 hydrosulphate were not in the state of bi-salts, they would not 

 begin to part with their acid till after having been brought to 

 that state. M. Henry has observed that the insoluble car- 

 bonates experience only a very partial decomposition by the 

 action of hydrosulphuric acid, and it is easy to conceive it ; 

 but it is not easy to conceive that the carbonates, according 

 to the same observer, should be decomposed with greater dif- 

 ficulty by the hydrosulphuric acid, than the hydrosulphates 

 by the carbonic acid. 



Akt. XXVI. — On an extremely Cheap and Delicate Hydro- 

 static Balance. By William Ritchie, A. M., Rector of 

 Tain Academy. Communicated by the Author. 



-Having been engaged in determining the ratio between the 

 weights and measures used in the counties of Ross and 

 Sutherland, and the new imperial standard, and not having 

 in my possession a balance of sufficient strength and delicacy, 

 I fell upon the following simple contrivance, which answered 

 as well as the finest hydrostatic balance. A balance of ex- 

 treme delicacy and accuracy, adapted to philosophical experi- 

 ments, generally costs fifteen, twenty, or even thirty guineas. 

 The expence attending the prosecution of physical science is 

 thus beyond the abilities of those who are best fitted for such 

 inquiries. The person who, by simple contrivances, will di- 

 minish the expence of such essential parts of philosophical ap- 

 paratus, will therefore confer an important benefit on the 

 young inquirer. With this view, I shall, through the me- 

 dium of this Journal, present the public with the description 



