standard metre should be lost or destroyed, it could not possibly be re-constructed, except in the same way. In theory it is supposed to be one ten millionth part of the length of the meridian passing through Paris from the equator to the pole. The length of this meridian was ascertained by estimation in French toises, made from several measurements of arcs in different countries. There is no certainty that a new estimation would be the same. Besides, the estimation itself is based on an old standard-the toise. The standard metre was made up of so many parts of a toise. It depends on the toise, and that has gone into disuse, and had no natural standard to govern its length. The certainty and uniformity of the metre, in fact, depends upon some one metalic bar in Paris, just as the certainty and uniformity of the yard depends, in practice, on another metalic bar in London. Destroy those metalic bars, and both the yard and the metre would have to be reproduced in precisely the same way.

The best standard, after all, would be the distance between two bolts driven into the face of some rock, and repeating the process in every civilized country, and in many places. These bolts being faced with a noncorroding metal, and having fine lines drawn perpendicularly through the centres, each country could measure the distance between these lines with its own standards. The distance might be sufficiently large to avoid the multiplication of errors, say ten, twenty or thirty feet, so as easily to be transferred from one country to another by means of a single rod. In this way a uniform measure could be preserved in the world for many ages; and each nation could, as occasion required, correct its own standard thereby.

It would undoubtedly be a matter of great convenience to have uniform weights, measures and money throughout the world, but it is a thing of very difficult accomplishment, each nation being wedded to its own long-used standards. There is no reason on earth why the English-speaking world should abolish their standards and adopt the French. For me, it excites my disgust and indignation to see our sciolists in their written articles using the metre instead of the foot and yard. Our literature and our statistics for a thousand years are pervaded with references to our own standards. Our ideas are all graduated to them by habit and usage. Why should we be frightened from our propriety by a set of French enthusiasts, who wish to have the general regulation of all things? If their metre had anything on earth to recommend it as a standard in preference to our yard, there might be some reason for joining in the cry for the Metric System. But it has not a single thing to give it such a recommendation. The decimal division, if that is thought desirable, is as applicable to our standards as to the metre. We all use decimals every day of our lives. I concur entirely in the views expressed by Sir John Herschel in his essay on the Yard, the Pendulum and Metre, and I hope that our volatile and changeloving people will never consent to the adoption of the French System.

July 3d, 1880.

THE FORCE OF WATER AS USED IN HYDRAULIC

MACHINERY IN MINING.

The circumstances which led to this publication are detailed in the following letter from Mr. Justice Field to ex-United States Senator James G. Fair:

WASHINGTON, D. C., February 23, 1891. HON. JAMES G. FAIR.

DEAR SIR: Last evening I dined at General Schofield's and met the President. There were a number of distinguished people present besides the President, among whom were the Chief Justice, the Speaker of the House of Representatives, Senators Sherman, Stanford and McMillen, Secretary of the Treasury, Windom and Mr. McKinley and Mr. Wheeler of the House. During the evening the conversation turned upon California and her wonderful products and mining operations. I took occasion to speak of hydraulic mining and the wonderful manner in which the hills are torn down by hydraulic machinery. I stated that I had understood you to say that such was the force of the water thrown through a hose, when it came from one to two hundred feet in height, that boulders weighing half a ton could be held* (moved) by streams playing upon them, and that the force was sometimes so great that it would be impossible to cut the stream. At this statement much surprise was manifested, and I thought a smile of incredulity passed over the features of the guests. Seeing this, I said that I would prove the facts stated in a communication to them.

Now, I write to you for the information desired. Please send me some carefully prepared statistics as to

E

STUDIES,

hydraulic mining, particularly as to the power exerted
by a column of water thrown by such machinery, and
as to how large boulders can be held* (moved) by the
force of the stream, and on the point whether it is true
that the force of the stream is sometimes so great that it
cannot be cut. I would be much obliged if
you could
give me full particulars in regard to these matters in a
communication that I can use, if necessary. I propose
to send a letter to each one of the guests, stating the
facts, and thus remove the incredulity which they
evinced when the statement was made by me. I want
to show that it was only the result of a want of
experience in hydraulic mining, their situation being
somewhat like that of the King of Siam, who was
offended when an English visitor told him that in his
country water was often so hard that he could walk
upon it.

Please let me hear from you at your earliest convenience, and believe me to be,

Very sincerely yours,

(Signed)

STEPHEN J. FIELD,

Not having received an answer from Mr. Fair, on account of his illness, Mr. Justice Field wrote a similar letter of enquiry to Augustus I. Bowie, Esq., of San Francisco, the author of a work of great learning and merit on "Hydraulic Mining "; and also another letter of the same character to Mr. Christy, Professor of Mining and Metallurgy in the University of California.

"Moved" instead of "held " was what was meant; as the very force striking the boulder would put it in motion instead of keeping it in repose, unless special preparation were made for the impact, as stated in the letter of Prof. Christy.

Subsequently a letter was received from Mr. Fair, enclosing one on the subject from Mr. Glass, who for sixteen years had been superintendent of a hydraulic mine in that State, and also the following

LETTER FROM MR. JUSTICE BRADLEY OF THE U. S.

SUPREME COURT.

WASHINGTON, D. C., March 5, 1891.

DEAR JUDGE FIELD:

The velocity of water issuing from a pipe is, of course, due to the pressure it receives-natural or artificial. If derived from a natural head of water, it is proportional to the square root of such head or height. If it were not for the resistance from the friction of the pipe and contraction of the vein as it issues from it, the velocity would be eight times the square root of the height in feet, or, more accurately, 8.025 times. The resistance varies according to circumstances. If the water has to be carried a long distance in the pipe, or if the pipe is rough or crooked, it is considerable. Supposing the reservoir near, and the pipe favorably arranged, the velocity will be 75 per cent. of the theoretical amount, or six times the square root of the height. Thus, suppose the head to be 450 feet; its square root is 21.2, multiplied by 6, it equals 127.2 feet velocity per second. If the crosssection of the pipe were equal to one square foot, this velocity would produce a discharge of 127.2 cubic feet per second. A round pipe, 6 inches in diameter, having a cross-section of only .19635 square feet, would discharge only 24.975 (say 25) cubic feet per second.