106 Notice of some Recent [Feb. 



year, and a mean struck of the whole observations. The 

 altitude of a mercurial column has been noted, and the 

 density of the air has thus been applied to discover the 

 temperature, by means of calculations which are sufficiently 

 well known. The temperature of deep springs has been 

 considered as an index of the mean temperature of the 

 locality in which such aqueous sources occur. 



These methods, however, do not apply equally well to 

 small as to great elevations above the level of the ocean. 



The depth at which an invariable temperature is met 

 with, varies in different situations. M. Arago found that 

 at 25 feet, (26*6 English feet,) below the surface of the 

 earth, the thermometer was not steady, and did not indi- 

 cate a constant mean temperature. This may be ascribed 

 to the influence of the variable atmospheric temperature. 

 Taking advantage of this inference, Boussingault conceives 

 that in climates where the temperature is tolerable equable, 

 the earth can be affected to but a very slight extent by 

 slight alternations of heat, as happens in equinoctial situa- 

 tions, {Ann. de Chim. liii. 225.) In 1830, during his resi- 

 dence at Vega de Zupia, he instituted a set of experiments 

 with the view of settling this point, and came to the con- 

 clusion, that in less than an hour, a traveller may ascertain 

 the mean temperature of any place between the tropics, 

 whatever its elevation above the level of the sea may be. 

 To prevent the effect of atmospheric influence, he experi- 

 mented under cover of a cottage or in the shade. The ther- 

 mometer was introduced into a hole, which was deep enough 

 to allow the bulb to be a foot below the surface, the hole was 

 then closed up by a bit of paper or other convenient sub- 

 stance. The temperature of Zupia was thus found to be 

 between 21°3 (70°3 F) and 21°5 (70°7 F,) which it must be 

 admitted is a close approximation, considering that the 

 observations amounted in number to twenty. At Marmato 

 the thermometer placed 1 foot below the surface, 1426 

 metres above the sea, ranged between 70 o, 3 and 70°7. In 

 the Valle de Cauca, 1050 metres above the sea, the range 

 of seven observations was 23°6 (74°4) and 23°8 (74°8.) 



At Purace, 2651 metres of elevation, the thermometer 

 placed in similar circumstances stood at 13°1 steadily, 

 during six observations on two separate (lays. At Quito, 

 with an elevation of 2914 metres, the mean temperature 



