for both steam and hand steering, and either the use of the ordinary cycloidal gear-wheel or the noiseless friction wheel for transmitting the power to the drum.

When the latter is employed, provision is made for taking up the wear of the friction wheel by resting the bearings B and B on keys or wedges as shown on Fig. 2, that can readily be backed, and the friction between the faces can then be regulated to any desired amount by setting on the cap-bolt nut. In the opinion of the Board the device is simple and ingenious in design, consists of few parts, is not liable to get out of order, and acts with celerity and precision; again, as the parts of the steam-steerer are so proportioned that the movement of the steam hand-wheel is identical with that of the ordinary steering gear, any one who can steer a vessel with the ordinary wheel can have no difficulty in steering with the device, however unfamiliar he may be with the manipulation or use of machinery.

Although the Board is of the opinion that the Steam Steerer in question will be found upon trial to be a valuable and reliable device for the purpose for which it was designed, yet it cannot recommend its purchase for use in the Naval Service until it is proved so to be by a thorough practical trial in steering a vessel under different conditions of wind and sea, and to that end the Board recommends that a Steam Steerer, of the above design, be purchased and fitted on board some sea-going vessel of the Navy for trial.

We are, sir, very respectfully, your obedient servants,

BOOK NOTICES.

No publication will be noticed under this head unless a copy for the Institute Library is sent to the Secretary, at Annapolis, Md.

A PAPER ON TIDAL THEORY AND TIDAL PREDICTIONS. By E. A. Gieseler, Superintendent of Construction, Fourth Light House District.

The first part of this paper contains an exposition of the Newtonian Theory of the Tides, and describes concisely the phenomena which naturally result at any point of the earth's surface upon this theory, as the sun and moon vary their relative positions, and their distances from the earth and from the zenith of the observer. The second part of the paper is on Tidal Predictions. The system proposed for predicting time of high, or low, water for any individual case consists simply in adding to the mean lunitidal interval of high, or low, water, certain corrections for the hour of the moon's transit, for declination, and for parallax of the heavenly bodies.

By means of several thousand tidal observations at Cape Henlopen, Delaware Bay, the corrections in time and height of tides at that point, for hour of moon's transit, declination of sun and moon, and lunar parallax have been determined. The general method of deducing these corrections consists in grouping the observations in such a way that two groups will render means in which the sidereal conditions are alike with one exception. Then the inference is justified, that the difference, either in time or height of the tide, found in the means of the observations is due to the difference in that one of the sidereal conditions which differs in the two groups. For example, in two groups of observations the hour of moon's transit and the lunar parallax are nearly the same, but the sun's declination differs, therefore the difference observed in the time and height of the tide is ascribed to the variation in the sun's declination. All the corrections deduced in this way are tabulated, and are used in predicting the time of high or low water, as follows:

Prediction of the time of high water at Cape Henlopen on the morning of May 27, 1884:

(1) Astronomical time of generating lunar

transit.

May 26

14 hrs. 191⁄2 m.

Time of high water as actually observed.......... May 27 IO

232 23%1⁄2 A. M. 15 A. M.

The system is minutely and fully explained and illustrated. If developed, it will supply much useful information in regard to the tides.

THE CRUISE OF THE ALBATROSS.

B. F. T.

This pamphlet, published by the Mittheilungen a. d. Gebiete d. Seewesens, Pola, gives an account of a fourteen months' cruise of this Austrian gunboat in the Red Sea and in East Indian and Chinese waters. The first part is devoted to hydrographic and meteorologic information in regard to the various ports

visited, and to sailing directions for the passages between them; while the second part treats of the commercial statistics of the ports with descriptions of them. Track charts are appended.

HAND-BOOK OF THE HOTCHKISS RAPID-FIRING GUN.

R. S.

This pamphlet, issued by the Hotchkiss Co., is most valuable. It contains complete descriptions of the three calibres now in use, together with directions for mounting and dismounting, care and cleaning required, nomenclature and description of the ammunition, nomenclature and description of the Non-Recoil Mount, gun exercise for the three calibres, stations for the care and cleaning of the guns, a chapter on accidents to mechanism, and an aiming drill with full directions for the training of the crews in marksmanship. Firing and penetration tables are also given, and a table of weights and measurements.

R. R. I.

DIE DEUTSCHEN UNTERNEHMEN IM SYSTEME der InterNATIONALEN POLARFORSCHUNG. Berlin, 1884.

The contents of this volume are taken from the Proceedings of the 4th German Geographic Congress, which was held in Munich, in 1884. Dr. Neumayer in the first paper briefly reviews the work done at German stations, especially at the stations on Cumberland Sound at Kikerton and Kingawa Fjord, in 1882-3, under the command of Dr. Giese, and that at the South Georgian Islands under Dr. Schrader. These stations were established under the auspices of the German Polar Research Commission, and the results of the observations are briefly indicated by Dr. Neumayer. The paper concludes with an earnest plea for concerted action by the different governments in establishing observation stations in the polar regions. The remaining papers, by Captain Koldewey, who commanded the Germania expedition in 1869 and 1870, and Dr. Börgen, are devoted to a resumé of what has been accomplished by Arctic research up to the present time, and insist on the further exploration of the Arctic regions and the establishment of international stations for this purpose. The further exploration of Greenland and its coast is especially recommended. J. T. S.

NORTH POLAR REGIONS. CHART OF THE ARCTIC Ocean.

The above is the title of an excellent conical projection recently issued by the Hydrographic Office, Navy Department, Washington, D. C.

The usual meridians and parallels are omitted, there being only two meridians at right angles to each other and one longitude circle projected. The lettering of all names is placed horizontally, so that all may read from one position without turning the chart. We are pleased to see that the route which has attracted the greatest attention, namely, the Smith Sound Route, is immediately before the observer when the chart is naturally placed, and that Cape Washington is marked as the most northern land yet discovered. The converging coast-lines of Greenland indicate more clearly on this chart than on others the probable insular character of that remarkable land. The latest Arctic discoveries are clearly shown, and the chart is another creditable evidence of the progress of the Hydrographic Office. J. W. D.