BioKEETON. — On Refrigeration. 395 



which butter and cheese may be kept for a sufficient time to enable their 

 transit to be made. Doubtless, the question of time is a very important 

 one, as it may be found possible to carry them with little trouble in a steam- 

 ship, whilst the uncertainties of the tropical calms may result in complete 

 failure with a sailing ship. A careful investigation into all these matters 

 would doubtless well repay its expense. 



In practically carrying out any method of reducing temperature, we are 

 met with the difficulty that air, when cooled, will generally deposit moisture ; 

 yet a most important point in the keeping of cheese is that it should be 

 dry. Therefore, in all our processes we must associate drying the air with 

 its refrigeration. There are two different methods of cooling a chamber, 

 and each of these methods will require a different mode of drying the air. 

 These two modes are either by replacing the air by cooler air or by cooling 

 the air already in the chamber. When fresh air is admitted the drying 

 may be effected by passing the air to the bottom of the chamber down a 

 thin copper tube inside the chamber. It will thus part with its heat to the 

 chamber, becoming warmer and consequently drier. As this tube would 

 be much cooler than the air in the chamber, dew would probably be 

 deposited on the outside. Means should be taken to catch this as it trickled 

 down the tube. This would tend to dry the air inside. 



If we adopt the method of cooling the air already in the chamber, this 

 will have to be effected at the top, and all that will be necessary to dry the 

 air inside will be to make arrangements to lead away the dew that will be 

 deposited on the coolers. These two methods are extremely simple, and I 

 believe would prove perfectly satisfactory. 



Before it could be determined which would be the best method for pro- 

 ducing the refrigeration, careful quantitative experiments would be necessary. 

 In this paper I shall only give the outlines of the modes of applying each of 

 the principles already mentioned, leaving it to experience to decide which is 

 best. 



If freezing mixtures be used, it would probably be best that the air 

 already existing in the chamber should be cooled, only introducing fresh 

 air occasionally. To cool the air, holes should be made in the roof and 

 large thin copper pipes closed at the bottom should be fitted into them. 

 The mixture should be placed in another slightly smaller similar vessel and 

 slipped down into the inside of the other upper tubes and stirred in situ. 

 The heat required to allow the salts to dissolve would come from the inside 

 of the chamber. The dew that was deposited on these tubes should be 

 caught in receivers fixed on the bottom of the pipes. This action as already 

 stated would tend to keep the air dry. As the air was cooled by contact, it 

 would fall by convection and be replaced by warmer air, 



