of the Movements of the Barometer. 21 



its subtraction or precipitation must also diminish the elasticity of 

 the remaining portion of the air, and, in this manner especially, 

 lower the barometer ; and this effect will be the greater in conse- 

 quence of the atmospheric vapour being accumulated, and its 

 precipitation chiefly effected, in the lower region of the atmo- 

 sphere, in which the movements of the barometer are consequently 

 observed to be proportionately greater than in more elevated 

 situations. 



In conclusion, I would observe, that as I should probably never 

 have taken the pains with this subject which I have done, but 

 with the view of laying it before our little Society, so my wishes 

 will be fully attained if this paper either excite interest or afford 

 instruction even to the youngest of our members, and thus tend to 

 further the object of our meeting together. My great aim, indeed, 

 has been to allure and aid the beginner in philosophical studies ; 

 and such, I imagine, to be the specific design of our institution. 

 With this view conjectures and observations which might otherwise 

 never have deserved attention become extremely valuable. — If any 

 further apology were required for the preceding pages, I would 

 say that the current of my studies has of late years flowed in a 

 totally different channel from that of philosophy ; but that it was 

 only by recurring to the studies of former days that I could select 

 any subject which would be appropriate to the present occasion. 



Art. IV. Description of an Instrument for destroying 

 Stone in the Bladder. By J. R. Griffiths, Esq, 



[Communicated by the Author.] 



I had long entertained the idea that an instrument might be con- 

 structed, by means of which a calculus in the bladder could be 

 broken down into fragments small enough to pass by the urethra, 

 and about three years since, with the assistance of an instrument- 

 maker, I attempted to put my plan in execution ; but not at that 

 time being able to construct a drill that would work in a curve, I 

 gave up the attempt. Some time after this I heard that an inr 



