466 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



hydraulic pressure ; this, mixed with some milk and water, 

 is churned, and the butter obtained is washed, and, if neces- 

 sary, melted. The authorities of the victualing department 

 of the French navy pronounce this an excellent substitute 

 for butter. 15 A, September 7, 1872, 309. 



FIRES CAUSED BY IRON RUST. 



A possible cause of fires is suggested by Colonel Angus 

 Croll in the following hypothesis: When oxide of iron is 

 placed in contact with timber, excluded from the atmosphere, 

 and aided by a slightly increased temperature, the oxide 

 parts with its oxygen*, and is converted into very finely di- 

 vided particles of metallic iron, having such an affinity for 

 oxygen that, when afterward exposed to the action of the at- 

 mosphere from any cause, the gas is absorbed so rapidly that 

 these particles become suddenly red-hot, and, if in sufficient 

 quantity, will produce a temperature far beyond the ignita- 

 ble point of dry timber. Wherever iron pipes are employed 

 for the circulation of any heated medium (whether hot wa- 

 ter, hot air, or steam), and wherever these pipes are allowed 

 to become rusty, and are also in close contact with timber, 

 it is only necessary to suppose that under these circumstan- 

 ces the finely divided particles of metallic iron become ex- 

 posed to the action of the atmosphere (and this may occur 

 from the mere expansion or contraction of the pipes), in or- 

 der to account for many of the fires which periodically take 

 place at the commencement of the winter season. 18 A, 

 January 12, 1872, 429. 



PAPER AND FIRE. 



The examinations of the books in the safes rescued from 

 the recent great fire in Boston have produced curious re- 

 sults. Paper considerably "clayed" stood the fire best. 

 Parchment paper used for legal documents was shriveled up, 

 and the printed and engraved lettering was so blistered that 

 it could be read when the writing was illegible. Books 

 packed tightly into a safe suffered less than those that were 

 set in loosely. In treating charred papers which could not 

 be made transparent by any kind of strong light, it was 

 found that the employment of sulphuric acid, oxalic acid, or 

 glycerine, caused the lines, words, and figures to become leg- 



