Ventilating them in Tropical Climates. 



227 



Description of Plate IV. 



A B C D Represents soldiers' barracks, with the ventilating machine placed 

 at the gable end. 



E The pipe conveying the cooled air, which enters the room through a hole 

 in the ceiling, w n a pipe connected with the hydrostatic pump P P, which 

 conveys the air to the pipe E, after having been cooled by passing through 

 all the contuiuous pipes of porous earthenware S S. In the pipe n n there 

 is a valve opening upwards, allowing the air to pass to E, but in no other 

 direction. 



B B A pipe connected with the funnel F, which is fixed on the top of the 

 house, in the same manner as that used over a malt-kUn, made so as aL^ 

 ways to present its open side to the wind. It is connected at the bottom 

 with the pipe n n, and at its junction has a valve opening down, so as to 

 permit the air to pass down from the funnel, but not upwards : this pre- 

 vents the air passing up through the funnel in a calm, when the gin is 

 used, and the other valve in the pipe n n prevents the air escaping through 

 the pump pp, when the funnel only is used. 



m m The fanners seen between the pipe S S, and round which they are coiled. 

 They are worked by the crank h h, which also works the pumps P P, by 

 means of the toothed-wheel o o, connected with the gin G G. 



On the Mountain-chains and Volcanoes of Central Asia, with a 

 Map of Chains qf Mountains and Volcanoes of Central Asia. 

 By M. DE Humboldt*. (With a Map.) 



V OLCANOES, which demonstrate a perpetual communication be- 

 tween the earth which is fluid, or in a state of fusion, and the 

 atmosphere surrounding its hardened and oxidated surface, are, 

 by their connexion with the formation of beds of rock-salt, with 

 Seises (small conical hills, which in their eruptions emit mud, 

 naphtha, gases unfit for supporting life, and sometimes also, but 

 only for a short period, flames, vapours, and blocks), with hot 

 springs, earthquakes, and the. upraising of mountains, an object 

 of so great importance for every thing which appertains to the 

 observation of nature, that they interest not only geologists, but 

 likewise natural philosophers, in the general acceptation of this 

 term. Leopold von Buch has already, in his great work on the 



• This memoir we consider of high importance, as illustrating not only 

 the geography, but also the geognosy, of several interesting parts of Central 

 Asia. 



