318 



as the proper source from which phosphorus, on the large 

 scale, is to be procured. On the small scale, shavings of 

 hartshorn were stated to be more convenient. 



Estimates were then given of the quantities of the ma- 

 terials to be employed under various circumstances, with their 

 cost, and the mode of manipulation. Directions were given 

 for recovering the acetic acid disengaged in the process, and 

 reconverting it into acetate of lead for future precipitations of 

 bone solutions. An easy method of drying and reducing the 

 volume of the phosphate of lead obtained was described. The 

 paper concluded with two formulae for obtaining phosphorus, 

 founded on the facts stated, which it was conceived reduce the 

 trouble and cost of preparing that article to the lowest scale of 

 which it is susceptible. 



Mr. H. L. Renny read a paper on the effects of moisture 

 as affecting the barometric measurement of heights. 



" Whereas Dr. Apjohn has inserted in a note of a paper 

 read by him before the Academy, and published in vol. ii. of 

 the Proceedings of the Academy (1840-1844), at page 565, 

 an expression for the correction due to the hygrometric state 

 of the atmosphere, in the formulae for the measurement of 

 heights by the barometer, which expression, as the note states, 

 was furnished to Dr. Apjohn by myself, I hope I do not re- 

 quest unnecessarily the attention of the Academy to the pro- 

 cess by which I obtained the said formula. 



Let p be pressure, ) . ^i. i x .• 



, ^ . ' }- at the lower station. 



f be the force of aqueous vapour, J g 



P " ' I at the upper station. 



/' be the force of aqueous vapour, J 



-\ at any station what- 

 TT be pressure, ' •' 



F be the force of aqueous vapour, 



« be a number extremely great. 

 8 be a quantity indefinitely small. 



*5 -' 



-\ at any station what 



/- ever, 7r and i^ being 



ir, I ' . = 



^ of course, variabk 



