642 PHILOSOPHICAL TRANSACTIONS. [aNNO 1755. 



which soon after invaded France, were very healthy all the time, when they 

 were very sickly in all the ships of that expedition. This certainly occasioned all 

 kinds of grain provisions to keep better and longer from weevels than otherwise 

 they wonld have done ; and other kinds of provisions received lienefit from the 

 coolness and freshness in the air of the ship, which was caused by ventilation." 



Mr. Cramond also informed Dr. H. that he found the good effects of venti- 

 lators on board a slave ship of his with 392 slaves, 12 of which were taken on 

 board, just before they sailed from Guinea, ill of a flux, which 12 all died ; but 

 the rest, with all the Europeans in the ship, arrived well at Buenos Ayres. And 

 a similar letter, on the good effects of ventilation, &c. was also sent by Captain 

 Henry Ellis, who mentions particularly that in one voyage in the year 1755, not 

 one of 3 1 2 slaves died ; and all his 36 sailors arrived alive and well at Bristol. Also 

 the Earl of Halifax often informed Dr. H. of the great benefit they found by the 

 use of ventilators, in several Nova Scotia transport-ships, 1 2 to one more have 

 been found to die in unventilated than in ventilated ships. It is indeed a self- 

 evident thing, that the changing the foul air frequently in ships, in which there 

 are many persons, will be a means of keeping them in better health than not 

 doing it. It is the high degree of putrefaction (that most subtile dissolvent in 

 nature), which a foul air acquires in long stagnating, which gives it that pesti- 

 lential quality, which causes what is called the jail distemper. And a very small 

 quantity, or even vapour of this highly attenuated venom, like the infection or 

 inoculation for the small-pox, soon spreads its deadly infection. 



LVl. Of Some Trials to cure the 111 Taste of Milk, which is occasioned by the 



Food of Cows, either from Turnips, Cabbages, or Autumnal Leaves, &c. 



Also to Sweeten Stinking ff'^ater, &c. By Ste. Hales, D.D., F.R.S. p. 339. 



The above method of blowing showers of air up through liquors, will be of con- 

 siderable use in several other respects, as well as in distillation, as appears by the 

 following trials, viz. 



Dr. H. had been informed, that it is a common practice to cure the ill taste of 

 cream from the food of cows, by setting it in broad pans over hot embers or 

 charcoal, and continually stirring it, till scalding hot, and till cool again. But 

 when he attempted to do this much sooner, and more effectually, by blowing 

 showers of air up through it, he soon found it to be impracticable, by reason of 

 its great degree of frothing up. The ill taste must therefore be got out of the 

 milk, before it is set for cream ; which he was told had been practised, and that 

 'vith some benefit, by giving the milk a scalding heat, without stirring it. 



May 22, He ventilated some ill-tasted new unhealed milk of a cow, which 

 was purposely fed with crow-garlic mixed with cut grass. After 15 minutes ven- 

 tilation the taste was a little mended ; in half an hour's blowing it was something 



