958 Transactions of the American Institute. 



Area of safety valve opening in. square inches per square foot of 



heating surface in boiler, j^r-, — r^ in which p. equals pressure in 



pounds above the atmosphere. This formula gives results corres- 

 ponding with those obtained by experiment for differences of 

 pressure, varying from one pound to one hundred pounds per 

 square inch. It is not strictly coiTect when the difference in 

 pressure approaches nearly to zero. The formula gives the area 

 required. to maintain the steam at a given pressure with fires burning 

 freely, but it should be remembered that a safety valve does not 

 open sufficiently to give its full area without considerable increase 

 of pressure. The area of the valve should, therefore, be much 

 larger tljan that of the opening calculated, as above shown. 



This formula also gives the proper size of the steam pipes con- 

 necting several boilers set in a " nest." The difference in pressure 

 in the iSeveral boilers should never exceed one-fourth of a pound at 

 the greatest; putting p — | in the above will give the smallest area 

 of steam connecting pipe consistent with safety, and it would be 

 better, when possible, to make them fifty per cent larger than this. 

 The limited S'ize of steam connections has been the cause of many 

 so-called "mysterious explosions" in a nest of boilers having but 

 one check-valve in the common feed-pipe. 



GEOMETRY IN NATURE AND ART. 



Mr. T. P. Pembertou read a paper with this title, of which the 

 following is a sketch: After speaking of the beautiful in nature, 

 the lecturer proceeded to describe the geometrical figures therein 

 displayed, and cited the forms of the planets and of their orbits. Of 

 the human figure he said: The whole body displays wonderful 

 mechanism and provision. The skull, as the casket that preserves 

 the brain, is spherical, or a hollow sphere. It is light and of the 

 strongest foiTn — capable of beai'ing a great amount of pressure, and 

 sustaining a superincumbent weight. The eye is elliptical; the nose 

 is traingular; the neck is cylindrical; the heart is a cone; the tapering 

 fingers are conical, and the bones themselves are hollowcylinders, 

 whilst the whole body in outline shows the most graceful and 

 beautiful curves: 



The proportions of the human figure are strictly mathematical. 

 The whole figure is six times the length of the foot. Whether 

 the form be slender or plump, this rule holds good. Any deviation 

 from it is a departure from the highest beauty of proportion The 



