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To the Editor of the SCIENTIFIC AMEBICAN: On the advice of a friend in the Bureau of Construction and Repair, I send you the following--the object being to bring the matter before the largest number of readers, in order that the error herein set forth may be corrected. I have been told that this argument of the great superiority of the dreadnought type over the older battleships mounting a less number of guns, owing to the shorter battle column, was first advanced by Capt. Sims of the navy, but I do not know whether this is correct. It is evident from an inspection of the diagram I send you that the argument, in the language of Prof. Tyndall, does not subtend a visual angle.* In a late issue of the SCIENTIFIC AMERICAN you mention the usefulness of the pre-dreadnoughts in forming a reserve division, which could be pushed forward after the engagement of the more powerful dreadnoughts with the enemy. Why not advocate more vigorous tactics? Place the antiquated battleships in the front when the battle is joined, and let them reduce the modern dreadnoughts and super-dreadnoughts of the enemy to a condition compelling them to seek their home docks for repair, and then bring forward your own dread-nought fleet to take command of the sea. WALTEB PEOCTOR JENNEY, PH.D. Washington, D. C. The Law of the Air To the Editor of the SCIENTIFIC AMERICAN: The popular acceptance of the aeroplane as a means of locomotion, and the firm belief of some of our legislators in vast increases in the number of these vehicles in the near future, is already leading to the enactment of statutes relating to their registration and regulation. Bills pertaining to aeroplanes have been prepared both in Connecticut and California, that in the latter State even specifying the lights to be carried. (See Aeronautics; March, 1911.) The aeroplane will doubtless be capable of speeds far exceeding the road speed of the automobile; and to it for this reason, as well as the impossibility of marking the illimitable aerial highways, State boundaries will be definite only so far as they are geographically evident. State regulation of the aeroplane spells a far greater nuisance, and leads to even more inconvenience, than does the State control of the automobile, the transfer of which to federal authority is occupying so much thought and. attention of prominent members of the automobile fraternity at the present time. Again, the State has not the legitimate claim to license fees for aeroplanes that it has for automobiles, based upon a damaging influence upon the roads. Let us have uniform laws for our aerial fleets, as we have a uniform marine code in all adjacent waters; and if State registration of aeroplanes is advisable for jurisdictional purposes, let it be, in all States, a uniform process, with a uniform registration fee, and being duly registered let the aeroplane * Belfast address. be free to pass across State boundaries, unhampered by local checks or regulations. If the foregoing be accomplished in these early days of aviation, the troublesome lesson of automobile registration will have served a useful purpose--the precluding of difficulties in one phase of interstate commerce, the extent of which is only a matter of conjecture. W. R. M. VEBY. Ithaca, ?. ?. The Thaddeus Stevens Industrial School We have received from Mr. William Mellor a letter which we publish below. We have much pleasure in giving publicity to this communication in our columns. Helping others to help themselves is the best form of philanthropy. Even from the purely commercial standpoint of public economy, such measures represent a most paying investment, making good citizens of persons who would otherwise, often through no fault of their own, be in danger of becoming a charge and a dead load upon the community. We may add to the statements made by Mr. Mellor in his letter, that, according to a circular issued by the Industrial School, admission of new scholars is made in April, an examination for admission being held about four months previous to this period. The subjects are reading, writing, arithmetic, geography, United States history, and composition. For further particulars address the school. Mr. Mellor writes: To the Editor of the SCIENTIFIC AMEBICAN: We are subscribers to your valuable journal, and I have thought that you might find it convenient through the medium of its columns to bring our school to the notice of poor boys in the State of Pennsylvania. The Thaddeus Stevens Industrial School is located in the city of Lancaster in Lancaster County. It is now engaged in teaching the following trades: Bricklaying, carpentering, patternmaking, and the machine trade. Boys to be admitted must be 16 to 18 years of age, having a common school education, of good moral character, and residing in this State. Poor orphan boys have the preference in the choice of admission. The course will require three years, during which time they are given clothing, board, lodging, one of the trades above mentioned, together with a good high school education. Knowing of the large circulation that your publication has among drawing rooms and shops, master mechanics, and workmen, I hope that it may reach those who know of some deserving boys who would be glad to avail themselves of just such advantages. Hoping that this will meet with your favor and notice, I remain, Respectfully yours, WILLIAM MELLOB, Superintendent. The Thaddeus Stevens Industrial School. Lancaster, Pa. Why Not Use the Moon to Drive a Machine ? To the Editor of the SCIENTIFIC AMERICAN The writer of this letter lays claim to advancing no new idea, but believes he is possibly presenting old ideas in a new light. The object being to divert a portion of a large amount of gray matter which is running to waste into a channel where it may eventually help turn the wheels of progress. Reference is made to the immense amount of mental effort expended on perpetual motion machines. My understanding of such a machine is one which gets its impetus from some natural force which is forever active. It is well known that a great many of these machines are founded on the assumption that it is possible for a ball in descending from one plane to another to develop more than enough energy to wriggle and twist a similar ball from the lower plane to the upper; the more complicated efforts ap-p e a r i ? g like attempts to sneak the ball up without the attraction of gravity catching them at it. As gravity has never as yet been caught napping, up to the present time there have been no successful machines recorded. But gravity is not the only force which is forever active. The attraction of the moon for everything on this earth is just as unremitting, with the great disadvantage that it is not so. appreciable, and with the great advantage that it acts from different directions at different times. An immense pendulum would oscillate in accordance with the position of the moon, but it would have to be housed on account of wind currents, and I never found in my astronomy a formula for computing how many miles high the building would have to be in order for the movement to be visible to the naked eye. But given such a building and such a pendulum, a machine, deriving its impetus from this pendulum and storing enough energy to keep it going during the time the pendulum would be comparatively at rest, would be as truly a perpetual motion machine as if it derived its energy from gravity. Nature has furnished us with several great pendulums in the oceans. A machine attached to these pendulums, which shall store enough energy to keep going while the tides are at rest, cannot possibly be disqualified as a perpetual motion machine merely because nature furnished us the pendulums. The men who are attempting to harness the tides are really experimenting with perpetual motion machines. Those inventors who are experimenting with perpetual motion would do well to devote their energies to making practical use of something which we have. Amsterdam, N, Y. A. F.
