NATURAL PHILOSOPHY. 153 



breaks in the clouds, was of a pale blue, such as is seen from the 

 earth through a very moist atmosphere. We were above clouds, but 

 there were no fine views or forms, all was dirty-looking and confused, 

 the atmosphere being thick and murky. 



"At the height of three miles a train was heard, and at four miles 

 another. These heights are the greatest at which sounds have ever 

 been detected, and indicate the generally moist state of the atmos- 

 phere." 



Mr. Glaisher concludes : " This ascent must rank amongst the 

 most extraordinary ever made. The results were most unexpected. 

 We met with at least three distinct .layers of cloud on ascending, of 

 different thicknesses, reaching up to four miles high, when here the 

 atmosphere, instead of being light and clear as it always has been in 

 preceding ascents, was thick and misty ; but perhaps the most ex- 

 traordinary and unexpected result in the month of June was meeting 

 with snow and crystals of ice in the atmosphere at the height of three 

 miles, and of nearly one mile in thickness." 



ASCERTAINING THE HEIGHT OF CLOUDS. 



At the British Association, 1863, Prof. Chevallier gave the following 

 description of an instrument of his invention, designed to ascertain the 

 height of clouds. It consisted, he said, of two jointed rulers, graduated 

 from the centre of the joint, and one of them furnished with an up- 

 right sliding-piece, with an opening to allow the sun's light to pass, the 

 edge of which is at a known distance by the scale from the ruler on 

 which the piece slides. If, then, the distance in miles or yards at which 

 the shadow of a cloud is cast upon the earth be known, by laying one 

 branch of the ruler toward the shadow of the cloud and the other in 

 the direction of the vertical line from the part of the cloud which casts 

 the shadow directly on the earth beneath the cloud, and then moving 

 the sliding-piece along this latter branch of the ruler until the shadow 

 of the edge of the opening just reaches the middle of the rod laid in the 

 direction of the shadow of the cloud, you have on the ruler and the 

 sliding-piece an exact representation in miniature of the actual circum- 

 stances of the cloud, and a simple rule-of-three calculation gives the 

 vertical height of the cloud above the earth. Thus, " multiply the 

 distance of the shadow of the cloud (supposed to be known) by the 

 height of the sliding-piece, and divide by the distance of the shadow of 

 the^sliding-piece from the angle of the rulers, and the quotient is the 

 height of ^the cloud required." 



OBSERVATIONS ON WINDS. 



Prof. Dove, the celebrated meteorologist of Berlin, in the second edi- 

 tion of his Law of Storms, recently published by the Longmans, of 

 London, thus explains his so-called " Laws of Gyration," or the rota- 

 tion of the wind in relation to the rotation of the earth. He says, 

 " In the northern hemisphere, when polar and equatorial currents suc- 

 ceed each other, the wind veers in general in the direction S., W., 

 N., E., S., round the compass. Exceptions to this rule are more com- 

 mon between S. and W. and between N. and E., than between W. 

 and N. or between E. and S. 



" In the southern hemisphere, when polar and equatorial currents 



