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 Rhode Island, New York, &c., 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 improvement, 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 formulæ 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 hydrocarbon a compound richer in hydrogen, the remnant of the distillation 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 process 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 ingredients, of which I will speak hereafter. 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

leum of a mean specified gravity of about 43° Baumé. When the crude petroleum is too heavy, the gaseous and very volatile products may be entirely absent, even to such a degree as to cause a loss for the opposite reason, leaving too large a quantity of tar, the result of an excess of non-volatile matter. Such oils are therefore used as lubricators. Besides this variety in crude petroleum, the petroleums of different wells (of which the fundamental formula is, as I will below explain, Cn Hn + 1, H) differ as much in the incidental substances they contain in solution or suspension as the water (of which the fundamental formula is H.) of different springs.

In the same manner as waters differ in containing salts of lime, soda, potassa, etc., or chlorides, bromides, iodides, sulphates, etc., so crude petroleums differ in containing oxygen or sulphur, nitrogen or phosphorus, arsenic, iron, etc. These incidental constituents, some of which are left behind, in the remnant of the distillation (the tar), have nothing to do with the chemical composition of the pure petroleum, the same as pure distilled water is independent of the incidental salts it contained before the distillation. Analyzing the tar or coke left from different kinds of petroleum demonstrates the presence of quite a variety of ingredients, which, however, will teach us as little about the nature of pure petroleum, as the analysis of the salts of mineral waters will teach us about the nature of the chemical composition of water; and even as eudiometric experiments are the most striking proof that pure water is H O, so eudiometric experiments prove that pure petroleum is CH, though with certain variable coefficients, which I will explain.

I intend later to publish a separate paper containing all the details of my quantative analysis, which would take up too much time, and besides be dry and uninteresting to most hearers. I will in the first place only state, that (as might be anticipated) the amount of hydrogen is largest in the first gaseous products of the distillation, less in the lighter fluids, as gasoline, naptha, benzine, still less in kerosene, and least of all in paraffine. These substances are all constant in their atomic constitution, although they are apt. to contain variable quantities of the volatile constituents of crude petroleum (as oxygen, sulphuretted, phosphoretted or arseniuretted hydrogen, etc.), always comparatively very small, but enough to give the distillates their strong characteristic odor. They are easily removed by concentrated sulphuric acid, which

also removes the oxygen often present in petroleum (as it is in water). Sulphuric acid, by its strong affinity to water, compelling all the oxygen in the petroleum to combine with part of its hydrogen, by which action water is formed and some carbon is separated; in fact this acid decomposes part of the hydro-carbons, as destructive distillation does, by robbing some carbon of its hydrogen, setting it free and coloring the oil black.

In regard to the relative quantities of carbon and hydrogen, I found the lightest kinds of the so-called gasoline of 96° specific gravity, to contain eighty-three per cent of carbon to seventeen per cent of hydrogen.

The liquid I discovered last year and called chymogene (cold generator), obtained by condensing by pressure and cold the gases escaping in vacuo, at the common temperature, consists of eightytwo per cent of carbon and eighteen per cent of hydrogen. The gases collected from the top of barrels coming fresh from the wells, are found to contain eighty to eighty-one of carbon and twenty to nineteen of hydrogen. Benzine contains about eighty-three and a half carbon to sixteen and a half hydrogen. Kerosene about eighty-four carbon to sixteen hydrogen; and paraffine, found long ago by others, a little over eighty-five carbon to a little less than fifteen hydrogen. Let us recapitulate these, and add the two extremes of the series, marsh gas C, H, and olefiant gas C, H.

Marsh gas contains in 100 parts.
Vapor from top of barrels, do

4

8

It is further found that the pure gasoline possesses all the properties of the so called hydride of butyle, of which the formula is Cg H10, and thus consists of forty-eight of carbon to ten of hydrogen, very near the relative quantities found above; that the gasce taken from the empty spaces in the barrels are very much like the so-called hydride of ethyle and propyle, as well in their chem