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SCIENCE. 



DR. D. DRAPER'S INSTRUMENT FOR RECORD- 

 ING THE VELOCITY OF THE WIND. 

 On the ends of a cross supported by a vertical shaft 

 several feet above the roof of the building, are four hem- 

 ispherical copper cups. These, whatever may be the direc- 

 tion of the winds, are caused to turn round with a speed, 

 as has been determined by experiment, of about one-third 

 the velocity of the wind. This portion of the contrivance 

 was the invention of Dr. Robinson, of Ireland. It is used 

 in the foreign observatories, and is known as Robinson's 

 cups. 



To the lower end of the shaft thus made to revolve by 

 the cups is attached an endless screw connecting with a 

 train of wheels, which move a cam. The wheels are so 

 arranged that one turn of the cam answers to 15 miles 

 in the movement of the wind. A pencil which rests on 

 the edge of the cam, and bears lightly against a surface, 

 is carried from the bottom to the top of the paper by each 

 revolution of the cam. It should be understood that the 

 paper is attached to a board drawn aside by a clock at the 

 rate of half an inch an hour. The number of times that 

 the pencil moves from the bottom to the top of the paper, 

 multiplied by 1 5, gives the number of miles that the wind 

 has moved in an hour or clay. 



The four hemispherical cups, a a a a, turned round by 

 the wind, impart their motion to a vertical shaft, b b, at 

 the bottom of which is the endless screw, c, its lower end 

 resting in a small agate cup filled with oil, connected 

 with the train of wheelvvork turning the cam, d d. At e, 

 is the pencil resting on the edge of the cam ; /"/ is a sheet 

 of ruled paper attached to the board, g g, by means of 

 small brass clamps, which is drawn aside at the above 

 mentioned rate by the clock, h. 



STATISTICS OF THE SUN. 



The following Statistics of the Sun, comprising facts 

 which can be stated in numbers, are selected from Pro- 

 fessor C. A. Young's recent work " The Sun," being one 

 of the last additions to Messrs. Appleton's International 

 scientific series. 



Solar Parallaxfequatorial horizontal), 8.80" ± 0.02" 



Mean distance of the sun from the earth, 92,885,000 

 miles, 149,480,000 kilometres. 



Variation of the distance of the sun from the earth be- 

 tween January and June, 3,100,000 miles, 4,950,000 kilo- 

 metres. 



Linear value of 1" on the sun's surface, 450.3 miles; 

 724.7 kilometres. 



Mean angular semi-diameter of the sun, 16' 02.0" ± 1.0". 



Sun's linear diameter, 866,400 miles; 1,394,300 kilo- 

 metres. (This may, perhaps, be variable to the extent of 

 several hundred miles.) 



Ratio of the sun's diameter to the earth's, 109.3. 



Surface of the sun compared with the earth, 11,940. 



Volume or cubic contents, of the sun compared with 

 the earth, 1,305,000. 



Mass, or quantity of matter, of the sun compared with 

 the earth, 330,000 ± 3000. 



Mean density of the sun compared with the earth, 

 0.253. 



Mean density of the sun compared with water, 1.406. ' 



Force of gravity on the sun's surface compared with 

 that on the earth, 27.6. 



Distance a body would fall in one second, 444.4 feet ; 

 135.5 metres. 



Inclination of the sun's axis to the ecliptic, J c 15' 



Longitude of its ascending node, 74. 



Date when the sun is at node, June 4-5. 



Mean time of the sun's rotation (Carrington), 25.38 

 days. . 



Time of rotation of the sun's equator, 25 days, 



Time of rotation at latitude, 20,° 25.75 days. 



Time.of rotation at latitude, 30. 26.5 days. 



Time of rotation at latitude, 45, 27.5 days. 



(These last four numbers are somewhat doubtful, the 

 formulas of various authorities giving results differing by 

 several hours in some cases). 



Linear velocity of the sun's rotation at his equator, 

 2.261 miles per second ; 2.028 kilometres per second. 



Total quantity of sunlight, 6,300,000,000,000,000,000,- 

 000,000,000 candles. 



Intensity of the sunlight at the surface of the sun, 

 190,000 times that of a candle flame ; 5300 times that of a 

 metal in a Bessemer converter; 146 times that of a cal- 

 cium light, 3.4 times that of an electric arc. 



Brightness of a point on the sun's limb compared with 

 that of a point near the centre of the disk, 25 per cent. 



Heat received per minute from the sun upon a square 

 metre, perpendicularly exposed to the solar radiation at 

 the upper surface of the earth's atmosphere (the solai 

 constant), 25 calories. 



Heat-radiation at the surface of the sun, per square 

 metre per minute, 1,117,000 calories. 



Thickness of a shell of ice which would be melted from 

 the surface of the sun per minute, 48^ feet; or 14^ 

 metres. 



Mechanical equivalent of the solar radiation at the sun's 

 surface, continuously acting, 109,000 horse-power per 

 square metre ; 10,000 (nearly) per square foot. 



Effective temperature of the solar surface (according to 

 Rosetti), about io,ooo° Cent.; or 1 8,000 Fahr. 



We have to thank our English contemporary the London 

 "Lancet" for its acknowledgement of the interesting na- 

 ture of the articles published in " Science." 



The Governor of Texas has taken steps to form a per- 

 manent organization preparatory to the establishment of a 

 State University. 



