PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 565 



These steam fire boxes will make one hundred pounds of steam 

 ■when attached to either cylinder flue or tubular boiler, before the 

 water in the boiler reaches the boiling point, when starting with 

 cold water and a bright fire. 



They can be attached to all kinds of boilers. Are in constant 

 use in some of the largest establishments in Ehode Island, New 

 York, &G., where they are attached to cylinder flue, hog-nose and 

 tubular boilers with equal success. 



After some discussion of the advantages of Mr. Miller's improve- 

 ment, the following paper was read : . 



Chemical Compositions of Petroleum. 



P. H. Vander Weyde, M. D., of Philadelphia : I have at last 

 succeeded in establishing beyond a doubt the formulfe for the 

 chemical composition of petroleum. As far as I am aware, all 

 that has been known about it, up to the present time, is the result 

 of the practical experience of distillers, who obtained liquid hydro 

 carbons of different degrees of volatility and specific gravity, a 

 portion escaping as gas, and in the remaining tar (containing the 

 non-volatile constituents), was also found a large amount of free 

 carbon in suspension, the product of destructive distillation : for, 

 as a high temperature has the tendency to distill from any hydro- 

 carbon a compound richer in hydrogen, the remnant of the distil- 

 lation will be richer in carbon, and at last be nothing but carbon 

 itself. — 



It is also known that the different products of the distillation 

 are very soluble in one another, so much so, that during this pro- 

 cess it is impossible to tell where one ends and the other begins; 

 in fact it requires repeated distillation to separate them, exactly 

 in the same way as it requires repeated distillation to separate 

 alcohol from water, which two substances are also very soluble in 

 one another. 



Further, it is known that the products of the distillation of 

 petroleums obtained from different localities do not differ in their 

 nature, as is the case with the crude petroleums themselves, but 

 are in general a uniform article, differing only in the quantities 

 obtained, in their perfect separation from one another, and in some 

 small amounts of flavoring ingredient*, of which I will speak here- 

 after. As regards the crude oil, when it is very light, exceedingly 

 volatile products are obtained in great quantity, to the loss of the 

 manufacturer of burning oil, who therefore prefers a crude petro- 



