352 History of Mechanical Inventions and 



to most advantage when placed high over a space not exceed- 

 ing sixty feet by twenty. " Air becoming specifically heavier 

 by being cooled, like every substance having weight, is pro- 

 jected farther from an elevation than along a level surface ; 

 and in the supposed (elevated) situation, it would keep sup- 

 planting what is constantly getting heated by contact with the 

 occupants, just as water when poured into the same vessel is 

 seen to displace spirit." One engine, requiring a single work- 

 man at a time, would suffice for an apartment of the dimen- 

 sions mentioned ; but Dr Ranken suggests that two should be 

 employed, facing in contrary directions, that either may be 

 resorted to when unmanageable draught stops the other. This 

 machine has been found so useful in allaying tlie heat up the 

 country, that it is, we understand, coming into more general 

 use than might have been supposed, considering the slowness 

 with which people adopt new inventions, however beneficial 

 they may promise to become. — From Asiatic Journal, vol. 

 xxviii. p. 32?5. 



S. Chinese mode of making Vermilion. 



Take quicksilver and sulphur, in the proportion of six- 

 teen taels of the former to four of the latter ; after powdering 

 the sulphur place them in an earthen jar, the outside of which 

 must be plastered with mud and salt to the thickness of three 

 inches and a half ; place an iron cover on the mouth of the 

 jar, and let it be kept constantly moist. Plaster the sides of 

 it so as to let there be no passage for air. Then place the jar 

 in an oven, with 120 catties of charcoal. Let this be done 

 early in the morning, and the next morning about the same 

 hour extinguish the fire, and at noon take it out of the oven, 

 and when cold break the jar in pieces, and take out the con- 

 tents. Pick out the dross, and then reduce the rest to a fine 

 powder. Let this be poured into a large jar full of water. 

 After a time a thin coating is found on the surface of the 

 water, which is carefully skimmed off, and a portion of the 

 water let off ; after a time this operation is repeated, the third 

 time all the water is drained off, and the sediment is then ex- 

 posed to dry, and afterwards taken out in cakes. This last 

 portion of the vermilion is called " the heart of vermilion." — 

 From Asiatic Journal, vol. xxviii. p. 326. 



