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boilers constructed of different kinds of iron; and, secondly, the methods of relieving them of too great pressure.

But the experiments that are requisite for attaining these ends require too great an outlay of money to be maintained at private expense. They need, and should have, the support of Government, especially as the Government attempts (very properly) to regulate the subject.

Experiments on the causes of boiler explosions were made about thirty-five years ago by the Franklin Institute of Philadelphia, and a report was made to the Secretary of the Treasury, who had furnished the funds. These experiments were made by a very able board, of which Prof. A. D. Bache was chairman. The results obtained and the deductions from them constitute nearly all that is now known on the subject of explosions and of the means of preventing them. This report has been published all over Europe, and forms the standard of reference. (See Report E, Doc. 162, 1st Sess., 24th Cong.) But these experiments were made upon model boilers of small dimensions, for the purpose of obtaining theoretical results as to the behavior of the structure under certain pre-conceived conditions. The trial of real boilers and the careful examination of boilers actually burst, and especially the reconstruction and testing of them under various conditions, was not attempted.

There have been as yet, in no country, any serious attempts made by trials and experiments on steam boilers of the size and kind generally used, to find the laws governing explosions; or to find the means of preventing them. From their dangerous nature, such

experiments cannot be made upon boilers in use; and the examination of the debris of an explosion generally adds nothing to our knowledge. The necessity of such experiments has been acknowledged in all countries where steam is employed; but the expense and difficulty of making them on actual boilers have prevented their being made. From a few experiments made at Sandy Hook in November last, upon boilers of different ages, in the presence of a large number of engineers, it became perfectly apparent that much is yet to be learned on the entire subject, and that intelligent and efficient legislation cannot be devised in reference to it until the investigation is prosecuted much farther than it has yet been. The probability is very great that, contrary to opinions frequently advanced, there are no forces acting in the explosions of steam boilers but such as can be controlled, and that in every instance, by proper experimental inquiry, the true cause can be ascertained.

The principal objects of a proper system of experiments would be the following:

1. To detect the faults in the ordinary construction of boilers.

2. To adopt more perfect means of preventing dangerous pressure.

3. To acquire such certainty as to the true causes of disasters by explosions that the penal laws on the subject may be strictly and intelligently enforced, and that thereby owners, constructors and those having charge of boilers may be more careful and diligent in the performance of their duties to the public.

In view of these considerations, it seems to me that Congress would do very wisely to authorize the Gov

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ernment to have a series of experiments made, under the charge of a board of skillful engineers, for the purpose of ascertaining those results, which the increased facilities of the engineering art would now render attainable.

I have the honor to forward with this a copy of the report made by Chief Engineer Isherwood and others of the experiments made at Sandy Hook in November last, to which allusion has been made. A more full report by Professor Thurston, illustrated by drawings, has been published in the Franklin Institute Journal.

I also forward the draft of law, or joint resolution, which would enable the President, through either of the executive departments, to institute the experiments which I have indicated.

I have taken an interest in this subject, and have presumed to address you upon it, under the belief that the experiments proposed would have more effect in producing the adoption of safeguards against the disasters continually occurring from boiler explosions than any regulations which can at present be made. The whole steam transportation of the country and of the world, and, indeed, the entire commerce of the world, is deeply interested in the ascertainment of the precise laws and exact data on which to calculate and provide for these disasters.

Respectfully, your obedient servant,

AN ACT TO AUTHORIZE INQUIRIES INTO THE CAUSES OF STEAM BOILER EXPLOSIONS.

BE IT ENACTED, etc.

SECTION 1. That the President of the United States be, and he is hereby, authorized to cause such experiments to be made and such information to be collected as, in his opinion, may be useful and important to guard against the bursting of steam boilers; and that he be required to communicate the same to Congress; and that the sum of one hundred thousand dollars be appropriated for the purpose of this act.

RECURRENCE OF ICE PERIODS IN THE NORTHERN HEMISPHERE.

1

491.13th

The absolute zero of temperature is -459.13 Fahrenheit, or 491.13 below the freezing point. This fact is deduced, amongst other things, from the law of expansion of gases, which is part of their volume at 32° Fahrenheit for each additional degree of temperature. Therefore the freezing point, or 32° Fahrenheit, is 491.13° above absolute zero. Supposing this to be the mean temperature, in New Jersey, on the first of January, when the earth is now in its perihelion, what would it be if the earth were in its aphelion instead of its perihelion on the first of January? This would depend on the relative distance of the earth from the sun at its perihelion and aphelion, and would be inversely as the squares of those relative distances. These relative distances are,

for perihelion 89,897,000 miles, and for aphelion 92,963,000 miles, so that the absolute heat derived from the sun in those two positions would be as (92,963) to (89,897). Thus, (92,963)' (89,897)'; 491.13° : 459.27°, showing a difference of 31.86°.

This would make the temperature of our winters about 32° less than at present. Ten thousand five hundred years ago the earth was in aphelion on the 1st of January.

STANDARD OF WEIGHTS AND MEASURES.

The English yard is the standard of measure in the British Empire and in the United States. The metre is the standard in France and in several European countries. The ratio between them is as 1 to 1.093633; or as 36 inches to 39.370791 inches. The yard is the more convenient of the two, corresponding better to the natural pace, and to the height and fathom of a man, two yards being equal to the height and to the fathom (or extension of the arms) of a man of full height. It can also be more easily reconstructed if the standard measuring rod should be lost. By Act of Parliament of Great Britain, it is declared that if the standard yard shall be lost, or destroyed, it shall be restored by making a new standard yard, bearing the proportion to a pendulum vibrating seconds of time in the latitude of London, in a vacuum, and at the level of the sea, as 36 inches to 39.1393 inches. This is the actual relation between them, and a new standard yard exactly equal to the present one could be constructed from a pendulum. But if the