TOL. XLIX.] ! PHILOSOPHICAL TRANSACTIONS. 643 



better. At the hour's end it had the same taste, but was sensibly better than the 

 unventilated milk. 



August 23, 4 quarts of ill-tasted new milk, from a cow, which had fed 84 

 hours on cabbage-leaves only, and drank during that time very little water, were 

 put into a leaden vessel, 8 inches in diameter, and 30 inches deep. The leaden 

 vessel was heated in a large boiler, and set into a vessel of hot water ; to give the 

 milk a scalding heat, and also keep it hot. In 10 minutes ventilation it was 

 perfectly cured of its ill taste; and after standing 24 hours in a broad pan, there 

 was a thick scum, which was half cream and half butter, free from any ill taste; 

 the skimmed milk was not sheer or thin : so here is a method to make good 

 butter from ill-tasted milk. The froth of the milk was so great, by reason of 

 a too brisk ventilation, as to make it froth over the vessel, which was 30 inches 

 deep; if it had not been kept down, by constantly lading and breaking the very 

 large bubbles of froth. But when the ventilation is more gentle, the froth has 

 risen but 3 inches from 6 quarts of milk, which was Q inches deep. The 

 cabbage milk was but 6 inches deep. He repeated the like operation the same 

 day, with the evening milk of the same cow ; but giving it only a heat, that he 

 could bear his fingers in, for a little time ; with this degree of heat, after 45 

 minutes ventilation, the milk, though much better tasted, yet was not so com- 

 pletely cured as the former milk. Hence we see how necessary heat is to vola- 

 tilize the rancid oil (which gives the ill taste) to such a degree as to cause it to 

 fly off by ventilation. It was observed, that what was milked from this cow a 

 week after she had done eating the cabbage, had an ill taste. He had not as 

 yet had an opportunity to try to cure, in the same manner, the ill taste of milk, 

 which is occasioned by cows feeding on autumnal leaves, or turnips. 



He ventilated 3 gallons of stinking Jessops well purging water. On first blow- 

 ing, the smell of the ascending vapour was very offensive, which oftensiveness 

 abated much in 5 minutes : in 1 1 minutes the smell was much better : in 20 

 minutes the water seemed sweet both in smell and taste ; and not sweeter at the 

 end of 45 minutes: 15 or 20 minutes will probably suffice. 



July 20th, 3 gallons of stinking sea-water were ventilated ; in 5 minutes it 

 was much sweetened, and no ill smell in the ascending air, though at first it was 

 very offensive: at the end of 10 minutes it had a small degree of ill taste; after 

 20 minutes no ill taste or smell. It frothed near a foot high during part of the 

 ventilation : this from the bitumen, &c. 



Some sea-water, which was made to stink with flesh and isinglass being put 

 into it, was not made perfectly sweet, not even by a ventilated distillation, and 

 an hour's more ventilation after it was distilled ; so that the putrefaction with 

 animal substances is not easily completely cured by ventilation. When the water 

 was 27 inches deep in the leaden vessel, no air could be blown up through it by 



4 N a ■■ " '' ' " 



