Scientific Intelligence, 6jC 315 



duce the sign + between the symbol of each salt. Thus, the 

 mineral species garnet which is not unfrequently a compound of 

 1 atom silicate of alumina 

 1 atom silicate of lime* 

 would have for its symbol Al° Si° + Ca° Si°, and the soda tartrate 

 of potash would be expressed by 



K°(4C2' : H)5o + Na°(4C2"H)5o. 

 This method of symbolical representation will, I trust, be found 

 to want some of the defects under which the previous ones have 

 laboured, and it seems peculiarly adapted to organic chemistry, the 

 dawn of which seems to be close at hand. 



I shall here conclude by apologizing for occuping so much of 

 your time and space. ^. 



V. — Nero mode of heating Apartments. 



At the Royal Institution on the 11th Instant, Dr. Arnot shewed, 

 that the expense of heating rooms in the usual way by an open 

 fire is enormous, in consequence of the waste of heat. In a 

 chaldron of coals, one half of the heat produced is sent up the 

 chimney, while the remainder radiates into the room; but one half 

 of this is also subsequently sent up the chimney, which is principally 

 occasioned by the width of that aperture. Hence, jths of the fuel 

 is actually wasted. In cold countries an open fire cannot be employed 

 because it is not capable of heating a room when the temperature of 

 the air is very low. Stoves are, therefore, used j but an objection 

 to stoves is that they become red hot and send too much heat up the 

 chimney. On this account they are often surrounded by porcelain 

 and brickwork. In manufactories, steam pipes and hot air are em- 

 ployed to impart a regular temperature to rooms, without which the 

 cotton yarn would be injured. Dr. Arnot tried to heat his library 

 by means of a hot water box communicating with the kitchen ; but 

 he found the expense ( £30) too great. He then thought of heating 

 the water in the box itself, and thus making it portable ; and, lastly, 

 he contrived a hot air box of simple construction which answers the 

 purpose completely. It consists of a square box of plate iron formed 

 of two chambers, which communicate at the top, capable of contain- 

 ing any quantity of air in proportion to the size of the room. 



On one side at the bottom there is a tube which conducts fresh air 

 into a small porcelain furnace enclosed in the box. This air after 

 supplying oxygen for combustion passes to the upper part of the box 

 and circulates into the posterior chamber where there is a chimney. 

 To prevent the air from becoming too hot, a valve is adjusted to the 

 I bomson'fi Mineralogy, i. 260. 



