412 



SCIENCE. 



[N. S. Vol. XIV. No. 350. 



One object well attained is success, and it is 

 to be hoped that the book will reach sufficient 

 sales through the reasonable accomplishment 

 of this object, so that the author may be en- 

 couraged to write another and more extended 

 volume which may meet the needs of the elec- 

 trical engineering students. 



The author is to be congratulated upon the 

 remarkable freedom of his first edition from 

 typographical errors. In other respects he is 

 perhaps not always so fortunate, as in some of 

 his definitions, which are not always adapted 

 to give a proper physical conception to the 

 student. Also, in certain parts of the book, 

 the descriptive matter is inexact or inadequate 

 — especially is this true in the chapter on 

 armature windings, where no attempt is made 

 to present the rational laws of windings, and 

 the short descriptions are inadequate and the 

 diagrams too small to be thoroughly serviceable. 

 Such faults, however, may be readily corrected 

 in another edition, the compliment of an early 

 demand for which we cordially wish for the 

 author. 



All in all, we heartily welcome the book to 

 a useful sphere and compliment the author on 

 his success. But we must regret that he did 

 not make a book which might occupy the 

 more important place of a scientific college text- 

 book on applied electromagnetism and the 

 construction of dynamos. 



DuGALD C. Jackson. 



DISCUSSION AND CORRESPONDENCE. 

 A NEW FIELD FOR KITES IN METEOROLOGY. 



To THE Editor of Science : Although kites 

 carrying recording instruments to a height ex- 

 ceeding three miles have rendered great ser- 

 vices to meteorology at Blue Hill and else- 

 where, they have been subject to the limitation 

 of requiring a wind that blows at least twelve 

 miles an hour. In certain types of weather — 

 notably anti-cyclones — the winds are light and 

 consequently observations with kites can rarely 

 be obtained at these times. It also happens 

 frequently that, while the wind at the ground 

 is sufiBcient to raise the kites, it fails completely 

 above the cumulus clouds so that the kites are 

 unable to penetrate this calm zone. 



By installing the kites and apparatus on a 

 steamship, not only can kites be flown in calm 

 weather, but observations may be made above 

 the oceans where little is known about the con- 

 ditions of the upper air. It is evident that a 

 vessel steaming twelve knots an hour through 

 a calm atmosphere will raise the kites to the 

 height they would attain in a favorable natural 

 wind, while the force of strong winds can be 

 moderated by steaming with the wind. In this 

 way, kites can be flown on board a steamer, 

 under almost all conditions and probably more 

 easily than on land, since the steadier winds at 

 sea facilitate launching them. Wherever these 

 observations in the upper air may be niade, 

 there is always a station at sea-level and not far 

 distant horizontally with which to compare 

 them. 



To test the practicability of this method of 

 flying kites, experiments were undertaken on 

 August 22, 1901, with the aid of my assistants, 

 Messrs. Fergusson and Sweetland, upon a tow- 

 boat chartered for this purpose to cruise in Mas- 

 sachusetts Bay. Anti-cyclonic weather condi- 

 tions prevailed, and a southeast wind blew from 

 6 to 10 miles an hour, but at no time with suffi- 

 cient velocity to elevate the kites, either from 

 sea-level or from the summit of Blue Hill., 

 With the boat moving 10 miles an hour toward 

 the wind, and within an angle of forty-five 

 degrees on either side of its mean direction, the 

 resultant wind easily lifted the kites and 

 meteorograph with 3,600 feet of wire to the 

 height of half a mile. 



While it is desirable to have a vessel that can 

 be started, stopped and turned at the will of the 

 meteorologist, as was the case in the experi- 

 ments described, it is nevertheless probable that 

 soundings of the atmosphere can often be made 

 from a steamship pursuing its regular course, 

 and such are about to be attempted by me on 

 a steamer eastward bound across the North At- 

 lantic. Although observations above all the 

 oceans are valuable, the exploration of the 

 equatorial region is the most important, since, 

 with the exception of a few observations on the 

 Andes and on mountains in central Africa, we 

 know nothing of the conditions existing a mile 

 or two above the equator. The need of such 

 data to complete our theories of the thermo- 



