NATUKAL PHILOSOPHY. 137 



frozen powder, placed in a mould, was squeezed to a sphere of hard 

 ice by the pressure. Cups were formed from the ice powder ; and in 

 the presence of such experiments it was easy to see how the snow 

 of the Alpine mountains should compress itself to ice, and how the 

 ice could be squeezed through the moulds formed by the valleys. 

 From existing glaciers the Professor passed on to those of a former 

 epoch, and showed that a diminution of the sun's heat would not 

 account for them. They were as much a proof of heat as of cold. 

 They were a proof of powerful condensation, but to produce the 

 vapor for condensation an enormous expenditure of heat was neces- 

 sary. To produce a glacier required as much heat as would raise five 

 times the weight of that glacier of cast iron to its melting point. 

 What was wanted, then, to produce the glacial epoch was not a less 

 powerful sun, but a more powerful condenser ; and the speaker con- 

 ceived that this was most easily obtained by assigning to the Alps a 

 greater mean elevation than they now enjoy. For ages they have 

 been planed down by glaciers and by atmospheric denudation gener- 

 ally. The valley of the Po is overstrewn with their ruins ; by the 

 wear and tear of time they must have been lowered, and hence ren- 

 dered incompetent to condense the vapors necessary to produce the 

 glaciers of a by-gone age. 



SCIENTIFIC BALLOON ASCENTS. 



Under the auspices of the British Association, eight balloon ascen- 

 sions for scientific purposes have been recently made by Mr. Glai- 

 sher, the well-known meteorologist. In a communication made to the 

 British Association, 1862, Mr. G. detailed the objects sought to be 

 attained in these experiments, as follows : 



The primary objects of the experiments were, the determination 

 of the temperature of the air and its hygrometric state at different 

 elevations, up to five miles. The secondary objects were, to compare 

 the readings of an aneroid barometer with those of a mercurial barom- 

 eter up to five miles ; to determine the electrical state of the atmos- 

 phere ; to determine the oxygenic condition of the atmosphere by 

 means of ozone papers ; to determine the time of vibration of a mag- 

 net on the earth and at different distances from it ; to determine the 

 temperature of the dew-point by Daniell's dew-point hygrometer and 

 Ilegnault's condensing hygrometer, and by the use of the dry and 

 wet bulb thermometers as ordinarily used, and by their use when un- 

 der the influence of the aspirator, so that considerable volumes of air 

 were made to pass over both bulbs at different elevations, as high as 

 possible, but particularly up to those heights where man may be resi- 

 dent, or where troops may be located, as in the high lands and plains 

 of India, with the view of ascertaining what confidence may be 

 placed in the use of the dry and wet bulb thermometers at those ele- 

 vations by comparison with those found directly by Daniell's and 

 Ilegnault's hygrometers, and also to compare the results as found by 

 the two hygrometers together ; to collect air at different elevations ; 

 to note the height and kind of clouds, their density and thickness, at 

 different elevations ; to determine .the rate and direction of different 

 currents in the atmosphere, if possible ; to make observations on 

 12* 



