592 Transactions of the American Institute, 



kilogrammes of sulphate of ammonia, two of carbonate of potash, 

 two of lime, but no phosphate of lime; to the sixth, no manure. 

 The return per hectare (nearly two and a half acres) was: 



On first piece 51.000 tons per hectare. 



On second piece 47.445 do do 



On third piece 25.034 do do 



On fourth piece 36.834 do do 



On fifth piece 37.881 do do 



On sixth piece 25.550 do do 



The increase of the first on the sixth was twenty-five and a half 

 tons, or just double. Beet root being sold at twenty francs per 

 ton, and artificial fertilizers at three hundred and ninety-five francs 

 per hectare, the profit was one hundred and fifteen francs by using 

 the fertilizer 



SPOTS ON THE SUN. 



Mr. Balfour Stewart, in a lecture before the Royal Institution, 

 London, on the sun as a variable star, expressed the opinion that 

 the spots on the sun's surface are produced by downward currents 

 of the surrounding atmosphere, the depth of which had been esti- 

 mated at not less than 72,000 miles. A downward rush of atmos- 

 phere occasioned an exposure of the body of the sun, and produced 

 an appearance of a dark spot; an upward rush of the atmosphere 

 produced the bright fecul^e that surround the dark spots, and are 

 seen more conspicuously on the borders of the sun's disc. This 

 atmosphere, he thought, was very sensitive to the approach of the 

 planets, especially of Venus, in consequence of its comparatively 

 short distance, and of Jupiter, in consequence of its size. When 

 Venus is opposite to the earth, the spots attain their maximum, 

 which is sometimes as much as 15,000 miles in diameter. From 

 these spots we estimate that the sun, rotates on its axis once in 

 about twenty-five days; but there is reason to believe that the spots 

 rotate faster than the body of the sun, owing to the more rapid 

 rotation of the upper portions of the atmosphere, which, on being 

 carried nearer to the center by a downward current, retains the 

 velocity it before possessed, in the same manner as the Trade 

 winds on the earth are supposed to be caused by the different 

 velocities of the air near the poles and in the equatorial regions. 

 In addition to the influencing causes attributable to the movements 

 of the planets, there are periodical variations of the spots occur- 

 ring about every ten yeai's, which cannot thus be accounted for. 



