Steam Engines in Corniuall. 233 



fore perceived tlie first tiling I had to effect was, to deprive them 

 as much as possible of those two bad qualities. I entered into 

 a variety of experiments, some of them long and tedious, which 

 I shall not take up vour time bv enumerating. 



1 began by washing the oil with spring water ; which is effected 

 by agitating the oil violently with a sixth part of the water. This 

 separates the particles of the oil, and commixes those of the 

 water intimately with them. After this operation, it looks like 

 the yolks of eggs beat up. — In less than fortv-eight hours thev 

 separate completely, the oil swinmiing at top, the water with all 

 feculent and extraneous particles subsiding at the bottom. I 

 improved very much on this, by substituting sea-water in the 

 place of fresh water. I tried whether fresh water impregnated 

 with salt, may not do as well as sea-water ; but found the light 

 not so bright, and of a reddish cast. — The oil which I haye 

 washed is rape oil, for which 1 am charged As. Ad. a gallon. I 

 have now made use of it constantly for two months : it gives no 

 bad smell, and when burning close to the spermaceti oil is not 

 to be distinguished. 



A friend of mine has calculated the expense of a lamp against 

 that of a pair of mould candles, and says the lamp is much 

 cheaper. After this, is to be compared the elegance of the one 

 against the vulgarity of tlie other. 



Count llumford estimated one patent lamp to give as much 

 light as four wax-candles, from the whiteness and brilliancy of 

 its flame. 



By the process of washing, the oil does not lose one-hundredtli 

 part. The experiment can at all times be made in a glass de- 

 canter. I purpose making it in a churn, with a cock at the 

 bottom, the water to come up very near to the cock, by \vhich 

 ail the oil can be drawn oft", after it has deposited its impurities.. 



I have the honour to be, sir, your very obedient servant, 

 Trabolgaii, IMarcli 1, 181G. EdwaRD RochE. 



STEAM ENGINES IN CORNWALL. 



By Messrs. Leans' Report of work done by steam-engines in 

 Cornwall, it appears that the average work of 20 engines re- 

 ported for August was 19,908,723 pounds of water lifted one 

 foot high with each bushel of coals consumed. And that, during 

 the same month, Woolf's engine at Wheal Abraham (with a loail 

 of 3 lib. 1 per square inch in the cylinder) lifted 28,933,734 

 pounds one foot high, and his other engine at the same mine 

 (loaded l.rl per square inch) 49,655,962 pounds one foot high 

 with each bushel ; and his engine at Wheal Vor (loaded 14*4 per 

 M|uare inch) lifted 40,098,9/0 pounds cne foot high with each 

 bushel of coals. 



THE 



