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for the backing. Your eye will quickly note which will be the better. Decide; place it on a pad and flatten by placing a piece of paper on top, and apply light pressure.
(b) Thoroughly clean the glass with ether-alcohol and absorbent cotton.
(c) Place a few drops of mercury on a clean blotter and thus remove any dirt.
(d) Place a drop of mercury on the part of the tin-foil which will not be used for actual backing. It will form like a blister. Raise the pad and enlarge blister by an inclined circular motion. Add more drops of mercury as necessary until the blister has extended over the entire tin-foil. Put the pad down on the desk. Take the sextant glass and gently slide over the mercury. Examine and see if clear of flaws. Then remove glass by sliding off and reclean. Some sediment will probably be found on the surface of the mercury. Again gently slide the glass over the mercury to the correct position, and if clear of flaws, turn up the outboard edges, place the pad in an inclined position to allow the excessive mercury to drain off and let backing set. At least twenty-four hours should be allowed.
(e) Collect the excessive mercury and put in bottle. It is essential that the part of the tin-foil where the mercury was first dropped on should not be used as the actual backing. For some reason this spot will crumble up and spoil the backing.
(f) When tin-foil has set, remove the edge and apply backing. In applying do not use a brush or anything that rubs. It will tear the tin-foil. Apply as you did the mercury to the tin-foil. Put on one drop and work it over the tin-foil by an inclined circular motion, until entirely covered. Be careful to just cover the observing edge, but thoroughly cover all the other edges. Then let backing set and dry.
It is well to practice first with a piece of glass about the size of an index glass, but watch the sharp edges. They are apt to tear the tin-foil. After a little practice you will be able to make perfectly satisfactory mirrors-so will your chief quartermaster.
Although the above will be found to be perfectly satisfactory, it is essential that the navigator should not allow his sextant to be unduly exposed, or his mirrors to get in unsatisfactory condition, but if they should and time be available, the above will be found to produce excellent results.
U. S. NAVAL INSTITUTE
The Board of Control announces the followPrize Essay ing awards in the Prize Essay Contest, 1919: Contest, 1919
First Honorable Mention to Captain Reginald
R. Belknap, U. S. Navy. Subject, “Military Character."
Second Honorable Mention to Lieut. Commander Beirne Saunders Bullard, C. C., U. S. Navy. Subject,“ Some Reflections on the Three Factors of Battleship Design.”
No Prize Essay has been awarded for the year 1919.
Elementary Steam Engineering by C. M. Book Reed has been published by the Institute and is Announcements ready for sale ; for table of contents see book
list. The Institute will publish the “North Sea Barrage,” a short photographic history of the U. S. Mine Planters' operations in the North Sea. The book will be ready about April 15, 1919, and sell for $3.00 per copy. The edition will be limited and the Institute will be glad to receive orders in advance.
The annual dues ($2.50) for the year 1919 are now payable.
Life, regular and associate membership, 5728. Membership
All members are urged to keep the Secretary and Address Treasurer informed of the address to which Pro
of CEEDINGS are to be sent, and thus insure their receipt. Members This precaution is now of particular importance as
notices of changes of stations are not now available for use of the Institute's staff.
Members and subscribers are urged to notify the Secretary and Treasurer promptly of the non-receipt of PROCEEDINGS, in order that tracers may be started. The issue is completed by the roth of each month.
The Institute Book Department will supply any Book obtainable book, of any kind, at retail price, postDepartment age prepaid. The trouble saved the purchaser
through having one source of supply for all books, should be considered. The cost will not be greater and sometimes less than when obtained from dealers.
The attention of authors of articles is called to Reprints of the fact that the cost to them of reprints other Articles than the usual number furnished, can be greatly
reduced if the reprints are struck off while the article is in press. They are requested to notify the Secretary and Treasurer of the number of reprints desired when the article is submitted. Twenty copies of reprints are furnished authors free of charge.
Authors of articles submitted are urged to furIllustrations nish with their manuscript any illustrations they
may have in their possession for such articles. The Institute will gladly co-operate in obtaining such illustrations as may be suggested by authors.
Original photographs of objects and events which may be of interest to our readers are also desired, and members who have opportunities to obtain such photographs are requested to secure them for the Institute.
Whole Nos. 145, 146, 147, 149, 155, 166 and 179 of Notice the PROCEEDINGS (March, 1913, Junė, 1913, September,
1913, January-February, 1914, January-February, 1915, and November-December, 1916, January, 1918) are exhausted; there are so many calls for single copies of these numbers that the Institute offers to pay for copies thereof returned in good condition at the rate of 25 cents per copy.
ANNAPOLIS, MD., January 15, 1919.
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