From perfect solidity to the greatest degree of fluidity of which the alloy was capable, required in the case of the first alloy given above, about seventy degrees of temperature: and between the temperature at which a solid could pierce the alloy, and the stationary temperature, was eight degrees. When the quantity of lead was doubled, the first interval was nearly one hundred and thirty degrees; and the interval between the temperatures of solidity and that at which the alloy could be penetrated easily, was about twenty degrees.

These facts show that in using fusible alloys, those should be preferred which contain the smallest quantities of lead: a similar reason would lead to the preference of those containing the smallest proportions of bismuth.

Tin is nearly liquid at the stationary temperature; hardens by plates or small masses, and becomes entirely solid at this same temperature.

Experiments were made to ascertain what quantity of bismuth could be added to tin without destroying the property just described. To one hundred parts by weight, of tin, one part, five parts and ten parts of bismuth, respectively, were added. The first alloy melted at 4393°, and had the general characters of tin in hardening; the second melted at 428°, and had these characters impaired; the third had no stationary temperature above four hundred degrees, and lost its fluidity by slow degrees.

As it was thus shown that alloys of tin and bismuth presented no peculiar advantages, the alloys for temperatures below 355°, Fah., were sought by combining the least quantity of bismuth which would give any requisite temperature with one of the alloys of the table on page 37. For this purpose the alloy of equal parts of tin and lead was selected as having appropriate characters in its solidification, and melting at nearly as low a temperature as any the others in the table. It does not, of course, follow, that this alloy when combined with a given quantity of bismuth, will produce as low a fusing point as some other would; a question which, if it were worth deciding, experiment would determine. A few trials on this head were made by the committee.

of

The following table gives the proportions of bismuth, which, added to an alloy of eight parts of tin and eight of lead, will give the temperatures of the stationary points of an immersed thermometer between 355° and 326°. With the alloy which terminates this table, the stationary temperature near the fusing point disappears, and another form of table is required for description.

TABLE II. Alloys of Tin, Lead, and Bismuth, melting between 355° and 326° Fah.

The stationary temperature having disappeared with the increase of bismuth, the points attempted to be ascertained were these; the temperature at which the metal began to lose fluidity; that at which it ceased to be a liquid, as indicated by the surface not returning to a level when indented; that at which the solid ceased to be penetrable to a small rod by moderate pressure; and when it became hard. As these temperatures present nothing as definite as the stationary temperature, they are, of course, only approximate. A few trials made on the withdrawal of a metallic stem from the alloy, showed that the temperature at which this ceased to be possible was, for the alloys in the following table, between the temperature at which the metal lost its fluidity, and that at which it could not be penetrated by moderate pressure.

TABLE III. Alloys losing fluidity between 313° and 246° Fah.

3.8 311 306 298 289 7.6 283 253 242§ 234

The fusing points of the metals used in the foregoing alloys were, of the tin, 442° Fah., of the bismuth, 506°, of the lead, 612°.

VI. To repeat the experiments of Klaproth, relating to the conversion of water into steam, by highly heated metal.

It being now well understood that an increase of temperature in a metallic surface may diminish the amount of vaporization of a fluid placed upon it, the object of the following experiments was to study the phenomena attending the vaporization of water by iron and copper, under different circumstances.

1st. To ascertain the temperature, at which a given small quantity of water will be vaporized in the least time, by copper, with different states of surface. 2d. To ascertain the same point for iron, in similar circumstances.

3d. To extend these deductions to the effect of introducing different quantities of water into copper or iron vessels, varying in thickness, in character of surface, and heated by different sources, to various temperatures.

A number of bowls, of these different metals, of as nearly the same figure as could be obtained, and of different thicknesses, were provided. The bowls were portions of spheres, of nearly three inches radius, and were eight in number, three being of copper and five of iron; four of these latter were of wrought, and one of cast iron. For applying heat to the bowls, a cylindrical vessel containing oil, and another containing tin, were provided; the former was about nine inches in diameter, and four high, and the latter six and a half inches in diameter and four high. These vessels were heated by Mitchell's* alcohol lamp, or in the very high temperatures, by a charcoal furnace. The bowls were furnished with handles, which projecting, overlapped the edges of the cylinders serving as baths for the oil and tin, and were thus kept in place.

The thermometers used in the experiments, were carefully compared at the boiling point of water, and melting point of pure tin.

The experiments first to be detailed, refer to the vaporization of drops of water in copper bowls of different states of surface, from the smooth polish to the roughness of oxidation.

Vaporization of Drops of Water by Copper.

1. The bowl, No. VII. of copper, seven-hundredths of an inch thick, was polished, but not very highly, and then placed in the tin bath while fluid; the tin, on solidifying, kept the bowl in its place. The thermometer was placed in a small cylinder of thin sheet iron, containing mercury, the cylinder being as near the cup as possible. As the experiments progressed, the surface of the bowl became, of course, more and more tarnished; and after the two series of results recorded below were obtained, a third showed a marked effect from the oxidation, by the increased vaporization. One hundred and twenty drops, nearly, from the tube used, made up one-eighth of a fluid ounce; the weight of one drop was, therefore, about .47 of a grain.

* A very convenient alcohol lamp, with a draught through the wick, and a separation between the alcohol reservoir and the wick.-The invention of Dr. J. K. Mitchell.

The temperature of maximum vaporization, under these circumstances, appears to have been between 3271° and 3293° Fah., the two series coinciding nearly in their indications; the repulsion is shown to have been perfect at 350, the drop falling upon the centre assuming the usual rotary motion, and disappearing very slowly.

2. The surface of this same bowl was next highly polished with rotten stone

In this and other tables, the series marked descending, are those obtained when the temperature was falling; the ascending series were obtained while the temperature of the bath was rising.

and oil, and a similar method of experimenting gave the following results, the same bath being used.

Reply to the Query in regard to the Coating of the Pipes forming the Condenser at the Philadelphia Gas Works.

TO THE COMMITTEE ON PUBLICATIONS.

Gentlemen,-Your correspondent, in his query proposed in the last number of this Journal, has fallen upon a disputed point of science; but I will endeavour to furnish the grounds for deciding his question, according to the conflicting authorities.

The object of the pipes, to which he refers, is to condense, in part, the moisture and other easily condensible matters, which come over with the heated gas from the retorts, previous to its entrance into the purifiers, where it circulates in contact with lime. This object is attained by a series of vertical