198 Dr. Bostock's Observations on [March, 



Silica 80 



Alumina 15 



Manganese 2*50 



Water 0-75 



Loss 1-75 



100-00 



This was the result of my own analysis. The analysis made 

 of the same substance by Mr. Holme, does not materially differ 

 from the preceding 5 and when it is considered how very seldom a 

 second analysis, made by the same person, of substances wherein 

 silica and alumina are chemically combined, exactly corresponds 

 with the first, it would perhaps better answer the purposes of 

 chemical science if the discrepancy were confessed rather than 

 concealed. At all events this shall* be the case in the present in- 

 stance. 



According to Mr. Holme's analysis of this mineral the same 

 constituents are combined in the following proportions : 



Silica 76-rV 



Alumina 20-jSg. 



Manganese. 2-\ 



Water 0-j-g. 



loo^ 



It has been stated that this mineral came from Sweden under 

 the name of petalite ; possibly it may not be the substance to 

 which Dandrada gave this name. Should this prove to be 

 true, as it will be necessary to bestow some name upon it, we 

 are desirous of calling it Berzelite, in honour of the illustrious 

 chemist who presides over the analytical researches of the 

 country in which it was discovered. 



I have the honour to be, Gentlemen, &c. 



Cambridge, Jan. 21, 1818. EDWARD DaNIEL ClARKE. 



Article VII. 



Some Observations on the Imperfection of the Barometer. By 

 John Bostock, M.D., &c. 



Being engaged, some years ago, in an inquiry respecting 

 the manner in. which the weight of the atmosphere is affected 

 by the blowing of different winds, and especially by the two 

 cardinal winds of this climate, the N.E. and S.W., I wished to 

 establish an accurate comparison between the height of baro- 

 meters in different parts of the island. In order to accomplish 



