CRITICAL NOTICES OP NEW PUBLICATIONS. 



250° Fah., a portion was thus forced out, in the liquid state, at 223*^ 

 Fah. The entire series of conclusions drawn by the Committee will 

 serve to indicate their train of experiment, for the numerical results 

 of which we must refer to the Report itself. 



"The conclusions deduced from the foregoing experiments on metallic 

 alloys may be thus stated : — 



"Ist. The impurities of common lead, tin, and bismuth, are usually not 

 such as to affect materially the fusing points of their alloys. 



" 2nd. When mixed in equivalent proportions, tin and lead formed alloys, 

 not presenting the characters of distinct chemical compounds, in definite 

 proportions. The alloys between the range of one equivalent of tin to one 

 of lead, and one equivalent of tin to six of lead, varied considerably in the in- 

 terval between the temperature of commencing to lose fluidity and that at 

 which the temperature of a thermometer, immersed in the solidifying metal, 

 became [for an instant] stationary. These different alloys produced nearly 

 the same stationary temperature in a thermometer plunged into the solidi- 

 fying metal. 



"3rd. Fusible metal plates, covered by a perforated metallic disk, and 



E laced upon a steam-boiler, show signs of fluidity at the disk before the steam 

 as attained the temperature of fusion of the alloy of which the plate is com- 

 posed. This fluid metal oozes through the perforations in the disk, and the 

 plate thus loses much of its substance before finally giving vent to the 

 steam. 



" 4th. The under parts of the plate are not kept from fusion by a protect- 

 ing film of oxide there formed. 



" 5th. The thickness of the plate is not important, provided only that it is 

 sufficiently strong to resist the pressure of the steam at temperatures below 

 its point of fusion. 



"Gth. The temperature at Avhich the plates are cast, and the rate of cool- 

 ing of the cast metal, do not affect the temperature at which the plates give 

 vent to steam. 



" 7th. The effect stated in conclusion third is explained by the nature of 

 the alloys used, which are formed of portions of difierent fluidities ; the more 

 fluid parts are forced out by the pressure of the steam, leaving the less fusi- 

 ble. These latter, in general, are burst, not melted. 



" 8th. By pressure in a receptacle provided with small openings this effect 

 of separating the differently fluid portions of an alloy may be imitated. 



"9th. Fusible alloys, used to indicate the temperature of any part of a 

 steam-boiler, should not be exposed to the pressure of the steam ; at least, 

 not in such a way that the separation of the differently fusible constituents 

 of the alloys may be effected." 



We shall return to this subject under the next head, to which we 

 now proceed. 



2nd. Explosions produced hy the presence of unduly heated 

 metal within a boiler. 



It was first observed, we believe, by the chemist Klaproth, that 

 when small drops of water were in succession thrown into a red hot 

 iron spoon, the first drops evaporated very slowly, and succeeding ones 

 disappeared more rapidly as the vessel cooled. These observations, 

 and others of an analogous sort, have been supposed to contradict the 

 conclusion that highly heated metal can produce steam rapidly, when 

 water was thrown upon it. M. Arago, in his Essay upon the En- 

 plosions of Steam Boilers, considers this as a capital difficulty to be 



