June 25, 1897.] 



SCIENCE. 



987 



'Navigation in Fog,' contains some in- 

 teresting suggestions regarding the pos- 

 sibility of determining the distance and 

 direction of one vessel from another in a 

 fog by means of a calculation based on the 

 velocity of sound. If, for instance, two fog 

 horns, A and B, are placed, one east and one 

 west of a given point in a north and south 

 channel, and each two miles distant from 

 the point, and these horns are blown simul- 

 taneously and automatically at regular in- 

 tervals of about a minute, a captain who is 

 trying to work his ship through the chan- 

 nel can readily get his bearings. Suppos- 

 ing that one horn has a higher pitch than 

 the other, and that a vessel is one mile east 

 of the channel between the two horns, the 

 captain of the vessel will hear the high- 

 toned whistle A five seconds after it is 

 blown, because it is only one mile distant, 

 but B will not be heard for 15 seconds, 

 since it is three miles oflf". If both horns 

 are heard together the vessel is in the mid- 

 dle of the channel. Another application of 

 this same method of determining positions 

 of vessels is suggested in the case of one 

 vessel attempting to pass another in a fog, 

 and in the case of the calculation of a ship's 

 distance from shore when the ship's time is 

 within a second or two of that on shore, 

 and when a whistle on shore is blown at 

 the exact beginning of each minute. The 

 determination of the velocity of the Mdnd is 

 also noted as being a useful application of 

 this same method, especially in the case of 

 very high winds, which are apt to injure 

 anemometers. Professor Pickering's sug- 

 gestions are worthy of serious consider- 

 ation. 



HYDROGEAPHIO OFFICE CLOTJD TYPES. 



The Hydrographic Office of the Navy has 

 issued a set of colored cloud views, classified 

 according to the international nomencla- 

 ture, for the use of its observers at sea. 

 There are twelve different views, printed 

 on one sheet, the whole sheet measuring 



23 X 28 inches, and the individual pictures 

 3Jx 5^ inches. These cloud types are not 

 reproduced from photographs, but from 

 paintings. The set is an admirable one, 

 some of the cloud forms being even more 

 typical than those in the new Cloud Atlas, 

 while the reproduction of the pictures of the 

 original views gives several of the pictures a 

 more natural appearance than the corre- 

 sponding forms have in the Atlas. The 

 alto-stratus, which in one of the views in 

 the Atlas is yellowish, has its proper color 

 of grayish-blue on the Hydrographic Office 

 sheet. The price of the sheet is 40 cents. 

 The views are also published on separate 

 pages, with descriptive text, bound, and 

 cost 60 cents in that form. 



RECENT PUBLICATIONS. 



On Obtaining Meterologieal Records in the 



Upj^er Air by Means of Kites and Saloons. 



A. L. EoTCH. Proc. Amer. Acad. Arts and 



Sciences, Vol. XXXII., No. 13, May, 



1897. 8vo. Pp. 245-251. 



An account of the kite work at Blue Hill 

 Observatory and of the ascents in Europe 

 by means of ' ballons sondes.' 

 Difference in the Climate of the Greenland and 



American Sides of Davis' and Baffin's Bay. 



R. S. Tarr. Am. Journ. Sci., Apr., 1897. 



Pp. 315-320. 



The Greenland side has the milder cli- 

 mate, owing to ocean currents and winds. 

 Meterologie. W. Geabert. Leipzig, 1896. 



Small 8vo. Pp. 149. 



Although much condensed, this new text- 

 book is well written and presents the newest 

 theories and facts. 



NOTE. 



Owing to the departure of the compiler 

 of these notes for a somewhat extended 

 scientific tour in South America, the reg- 

 ular publication of the Current Notes on 

 Meteorology will be suspended during the 

 next six months. 



R. DeC. Ward. 



Harvard University. 



