2,5* Description of a Safety Valve t 



Example 3d, for C. 



As the perpendicular height, 4 feet - fiOSOfi 



Is to radius, 90° _ - - 10-00000 



So is the horizontal distance, 18 feet - 1*23327 



n-23527 



To the co-tangent of the declivity, 12° 32' 10-65'321 



The annexed survey, Plate Vf. of a small lake and arti- 

 ficial mountain in the garden of his excellency count de 

 Strogonoff, near St. Petersburgh, has been closed by the 

 tables of the difference of latitude and departure as follows ; 



XLVII. Description of a Safety Valve, containing a Vacuum 

 Value in the same Hole of the Boiler*. 



Xn lar<'"e boilers or coppers, where boiling fluids are in- 

 closed, a safety valve is generally used to prevent their 

 bursting, from an unexpected excessive force of the elastic 

 steam, and, besides, a vacuum valve, to prevent their being 

 compressed or crushed by the weight of external air, in the 

 case of a sudden condensation of the vapours. These twq 

 valves are commonly fitted in two different holes in the 

 boiler; but as a more simple, and consequently more eligi- 

 ble method, seems to be that of joining them together, I 

 take the liberty to submit to the Society for the Encourage* 

 nient of Arts, &c. the fallowing contrivance for that pur- 

 pose : 



al>3 Plate VII. fig. 1, ia a common conical safety valve, 



"■■ From 'fiansfutionsi-f the Socicly of Arts, &,c. vol. xxii. — The silver 

 medal of tuc t.oci'.ty vas voice! to the author for this couimuiiication. 



ifixcd 



