230 FIRESIDE SCIENCE. 



chemical reagents, results regarding temperature, 

 moisture, and the presence of gases and extraneous 

 bodies in the room, were carefully noted. The 

 furnace was then removed, and the other one put 

 in its place. The same experimental labors were 

 undertaken with this during a period of four weeks. 

 As the details of these experiments require for their 

 proper presentation more space than can be afforded 

 in this essay, we will only allude to them in gen- 

 eral. 



The interior of the furnaces was made of cast- 

 iron, and the joints of the first were cemented with 

 a paste made of finely pulverized glass and plaster ; 

 the joints of the second were luted with a putty 

 made of sesquioxide of iron and linseed oil, and 

 over this the cement of glass and lime was spread. 

 The fire-pots were lined with brick. Every pre- 

 caution was used to render the joints gas-tight. 



The coal used was anthracite ; the two varieties, 

 " red " and " white ash," being mixed together in 

 equal parts. The experiments conclusively proved 

 that at no time were carbonic acid and carbonic 

 oxide absent from the library heated by the fur- 

 naces. During the days when a breeze was blow- 

 ing outside, causing a brisk draught, the amount of 

 these gases present was very small; but in dull, 

 moderate weather, the increase was quite percepti- 

 ble : carbonic oxide appeared to predominate, and 



