1885.] on the Mechanical Production of Cold, dc. 309 



much lower, and, in point of fact, to as low temperatures as have 

 yet been produced in physical researches. 



For the purposes of the conjoint experiments with Professor 

 McKendrick, a machine, worked by a gas motor engine, capable of 

 delivering 30 cubic feet of air (-84 cub. metre) per minute, was 

 employed, the cold air being made to pass upward in a square vertical 

 shaft of wood, in the sides of which were apertures regulated by 

 valves, and by means of which about a dozen chambers, each of 3 cubic 

 feet capacity ( • 084 cub. metre), could be maintained at any particular 

 temperature desired. These tem23eratures were carefully taken by 

 an absolute alcohol thermometer, made by Negretti and Zambra, 

 and checked by a special air thermometer devised by Mr. Coleman. 



The experiments consisted in exposing for hours to low tempera- 

 tures putrescible substances in hermetically sealed tins or bottles, or in 

 flasks plugged with cotton wool ; the tins or flasks were then allowed 

 to thaw, and were kept in a warm room, the mean temperature of 

 which was about 80^ F. (27° C.) ; they were then opened and the con- 

 tents submitted to microscopical examination with magnifying powers of 

 from 250 to 1000 diameters. The general results were as follows : — 



1. Meat in tins (4 J inches in diameter, and 1 inch in depth), 

 exposed to 80^ below zero F. ( - 63^ C.) for six hours, underwent 

 putrefaction with generation of gases.* 



2. Whilst these experiments were going on, comparative experi- 

 ments were made with tins and bottles containing meat, but not 

 exposed to cold. Under such circumstances, the efiects of storing 

 them in the warm room for even the short period of a fortnight, was 

 to develop such large quantities of extremely foetid gas, and very 

 active bacteria and vibrios, that there was no doubt whatever but 

 that exposure to a cold of 80° below zero (63° C.) had checked their 

 development to some extent in the subsequent exposure to a warm 

 temperature. 



3. On the 24th of December, 1884, thirty samples of fresh meat 

 were placed in 2-oz. white glass phials. These were carefully corked 

 with corks previously steeped in mastic varnish, and the necks of the 

 corked bottles were then immersed in melted sealing-wax. These 

 bottles were divided into five sets, and marked A, B, C, D, and E, 

 and they were treated as follows : — 



A. 6 samples were exposed to zero F. (- 17° C.) for 65 hours. 



B. 6 „ „ - 20° F. ( - 29° C.) 



C. 6 „ „ - 30° F. (- 34° C.) 

 r>. 6 „ „ -40°F. (-40°C.) 

 E. 6 „ „ -80°F. (-62°C.) 



* July 1885. — At this date, which is eight months from the commencement 

 of the experiment, several of the sealed -up tins are on hand ; the bulging of 

 the tins and apparently the generation of gases ceased after the first month 

 the organisms being apparently rendered inactive by their own effluvia, or 

 from want of oxygen. There is now very little smell on opening the tins, 

 but a large number of organisms are visible with a |-iuch object-glass— alive 

 and active. — [J. J. C] 



