SIO On the Cold Caves of the Monte Testaccio at Rome. 



cubic inch, and a degree of moisture (saturation being expressed 

 by 1.000) of S^Q. I then caused the iron-pipe of a pair of bel- 

 lows A, Plate IV. Fig. 1, to pass through an earthenware cylin- 

 der BB, to which it was firmly attached, and the interstice was 

 filled up with sand. The muzzle of the bellows and its case was 

 then heated, till the temperature of the air which issued from the 

 mouth on working the bellows was 80% and it was then placed 

 touching the lower orifice of a large glass jar C, having a wide 

 open neck D ; in the bottom of the jar were placed fragments 

 of pottery, moistened with water, at the temperature of the 

 room. A thermometer E, was suspended among the pots, just 

 at the lower tubulature of the jar, so that the bulb was only 

 about three inches distant from the orifice of the bellows ; these 

 arrangements having taken some time, the heated stream of air 

 was somewhat diminished in temperature. The bellows hav- 

 ing been worked for some time, the thermometer (which had 

 its bulb covered with paper and thoroughly moistened) was 

 stationary at 59-5. When the experiment was finished, the 

 stream of heated air was 74^ ; the air at the top of the jar, 

 shown by the thermometer F, was QGP^ and among the pots 

 62°, to which the air of the apartment had now risen. 



II. It then occurred to me that the experiment might be va- 

 ried in a more just manner. The air of the room was 62° A 

 moistened thermometer fell to 55^'^ hence the grains of moisture 

 in a cubic inch were .0022631, and the ratio to saturation .627? 

 or almost the same as before. The stream of heated air pro- 

 duced in the same manner, but very equably, was 81 J°. In- 

 stead of using the jar, it was made to pass through a porcelain 

 tube soaked with water, about eight itiches long and half an inch 

 in diameter, and at the farther end from the bellows was placed 

 the thermometer, moistened with water, at 62°. When the bel- 

 lows were worked, it fell to 60, or about half a degree higher 

 than in the last experiment, the stream of air being at least 4° 

 warmer. 



III. To take the simplest, and perhaps the truest, view of 

 the case, on an after occasion I caused a stream of air, heated 

 to 80°, to fall directly on the moistened bulb, placed at the 

 distance of only three inches from the muzzle of the bellows; 

 and by a separate contrivance, drops of water at 64°, fell re- 



