ON ARTIFICIAL REFRIGERATION. 959 



"Drying tiie air. — The liquid in tlie tank surrounding the tubes 

 through "svhich the air is blown can be readily kept at a point a little 

 above freezing, and the tubes are so i>laced on an incline that the moist- 

 ure condensed from the circulating air trickles back and is drawn off at 

 will. Condensation by cold surfaces is the cheapest and best method of 

 drying air. The evaporation from the hot meat helps to abstract the 

 animal heat, and when the meat is cold the continuous draughts of cold 

 dry air are most beneficial. 



" PuRiFYiNa THE AIR. — One effect of the constant circulation of the 

 air of the ship's hold through damp cold tubes is that it gets completely 

 purified, and germs of decay and of mould are arrested. The atmosphere 

 is sweet and pure, as well as cold, and this is one of the most desirable 

 results attained by the plan now devised." 



F.— DOES ICE DRY AIR? 



I then believed, as I do now, that great economies and certainty would 

 attend the use of antiseptics in conjunction with moderately cold air- 

 currents for long voyages, and, since I have been in America a second 

 time, I perceive that the crude ice method might have been attended 

 with less loss and difficulty, had the persons engaged in the business 

 acted under competent scientific advisers. So uncertain are they of the 

 principles under which they work that some believe ice dries, and others 

 that it wets air, whereas the truth is that ice condenses moisture from 

 damp air warmer than itself, but will give ivp moisture to dry air at any 

 temperature. Evaporation goes on from a surface of ice or snow at 32<^ 

 Fahr. In the open air, and in a perfectly still night, the moisture 

 amounts to nearly one ounce for every square metre exj)osed per hour. 

 At 0° Fahr. nearly a quarter of an ounce of watery vapor rises per square 

 metre per hour, and at 32^ below 0° Fahr. more than two j)Ounds of 

 invisible vapor ascend into the air from every acre of siu'face. Tliirteen 

 to fourteen hundred pounds of watery vapor pass into the atmosphere 

 for every square mile of snow or ice. 



Y.— PROPOSED IMPROVEMENT IN FREEZING FISH. 



It is to be regretted that immense sums are invested in carrying out 

 crude methods in the arts, and the introduction of rational and economi- 

 cal processes are then resisted by those who like to leave well alone. 

 This would indicate the advantages to be derived by a careful exposition 

 of the state of knowledge, in this case of the art of fish preservation, and, 

 having laid down the principles involved in all known processes, a solid 

 basis for further improvement might be established. Moreover, trials of 

 new devices, under carefully-noted conditions, without involving very 

 large outlay, might speedily enlarge the area of trade to the fisheries of 

 this or any other country. It is of course difficult, for a person engaged 

 in a large business, to change any system fairly meeting his requirements j 



