December 29, 1905.] 



SCIENCE. 



883 



Paper pilot balloons, to show wind direc- 

 tions and not carrying instruments, were 

 sent up and their height was obtained by 

 simultaneous angular measurements at the 

 end of a base-line on shore. Soundings of 

 this kind were made at Madeira, Teneriffe and 

 the Cape Verde Islands in particular, and also 

 over the open ocean. Observations were also 

 made on the peaks of Teneriffe and Togo, and 

 included the drift of clouds above these peaks. 

 Tabulations of these observations, and a chart 

 showing the tracks of three balloons, make it 

 evident that the winds blowing equatorward 

 vary in direction between northeast and north- 

 west. The latter are usually above the north- 

 east stratum, the thickness of this layer of the 

 trades near Teneriffe being about 3,000 or 

 5,000 meters. Above this there are southeast, 

 south and southwest currents — the anti-trades 

 —of great thickness, probably, but of small 

 density. The east wind near the thermal 

 equator extends very high, as had previously 

 been inferred from the carriage of volcanic 

 dust and the movements of lofty clouds. The 

 southeast wind was observed by a balloon at 

 the Cape Verde Islands up as far as 6.8 miles. 



The results obtained during the past sum- 

 mer, therefore, confirm the accepted theory of 

 trades and anti-trades, and are not in accord 

 with the view advanced by Dr. Hergesell. 

 North of Madeira and towards the Azores the 

 upper winds, as already shown by cloud ob- 

 servations, are prevailingly from west and 

 northwest, this region being usually north of 

 the oceanic high pressure area and outside 

 the trade wind zone. The anti-trades, with 

 their southerly component, are generally 

 southwest in the latitude of the Canary 

 Islands and southeast near the Cape Verde 

 Islands, corresponding to the effects of the 

 earth's rotation. Upper cloud observations at 

 Havana and in the Antilles further prove the 

 existence of these winds. 



AN INSTRUMENT FOR DETERMINING TRUE WIND 

 DIRECTIONS AND VELOCITIES AT SEA. 



In the ' Report of the Imperial Academy 

 of Sciences of St. Petersburg ' for August, 

 1905, Mr. Rotch describes an instrument of 

 liis own invention which is designed to give 



the true wind direction and velocity on a 

 moving vessel at sea, an observation which 

 has always been difficult and troublesome. 

 The theory of this instrument is based on the 

 triangle of forces. It consists of two movable 

 discs, graduated into 360° each, and three 

 rulers, hinged so that they may be adjusted 

 to different angles. One of these rulers indi- 

 cates the direction in which the vessel moves; 

 a second shows the apparent, and the third 

 the true wind direction. To set the instru- 

 ment the direction of movement and the speed 

 of the vessel; the apparent wind .direction, 

 shown by the smoke from the funnel, and the 

 true wind direction shown by the waves, are 

 needed. When the rulers are set to accord 

 with these conditions, the true wind direction, 

 in degrees, and the true wind velocity, in 

 miles an hour, are shown by means of the 

 discs above referred to. 



Casella, of London, is the maker of the 

 instrument, the price of which is a^Dproxi- 

 mately £3. 



BRITISH RAINFALL, 1904. 



The forty-fourth annual volume on ' British 

 Rainfall,' compiled by Dr. H. R. Mill, in- 

 cludes the records of 3,982 rain gauges. In 

 his preface the compiler regrets that he can 

 not visit more of the stations, and notes that 

 the chief difficulty is the inadequate train 

 service in the rural districts. The effect of 

 the automobile's advent is noted in the state-' 

 ment that ' a few years ago the bicycle sup- 

 plied a quick and easy means of overcoming 

 the difficulty, but now, except for the fact 

 that it is not prohibited by law, cycling on 

 the high roads of England scarcely differs in 

 point of danger from walking on the railways.' 

 The volume contains an appreciative mention 

 of the valuable work done at Ben ISTevis Ob- 

 servatory since 1883, and now unfortunately 

 given up, and the frontispiece shows the sum- 

 mit of the mountain in winter. There are 

 other papers on subjects of more local British 

 interest, but we call attention with special 

 satisfaction to the charts showing the tracks 

 of cyclones which produced exceptionally 

 heavy rainfalls during the year 1904, the same 

 charts showing also the distribution of the 



