Mechanical Science. 137 



the cube will lose its angles and edges, and ultimately there will 

 be found at the bottom of the vessel all that has been detached 

 during the trial. The trial should be concluded at the end of the 

 fifth day after the salt has first appeared in crystals. The for- 

 mation of crystals may be facilitated by moistening the stone as 

 soon as they have appeared on any one point ; this may be re- 

 peated five or six times a-day. 



Great care should be taken that the saturation of the water by 

 the salt be effected at common temperatures. '1 he experiments of 

 M. Vicat and others have demonstrated, that stone, which resists 

 perfectly the action of frost or of cold solution of sulphate of soda, 

 gives way entirely when exposed to the action of a saturated hot 

 solution: the same is the case frequently also, if the trial be con- 

 tinued beyond the fifth day. Mortars and bricks which had with- 

 stood ten winters gave way to saturated hot solutions ; and M. 

 de Thury found that lias and other stones which had resisted the 

 weather for ages, were disintegrated by the same excessive kind 

 of trial : from which it may be concluded, that stones which can 

 resist these trials would scarcely undergo any change by expo- 

 sure to weather for any length of time. 



If it be required to estimate comparatively the power possessed 

 by two or more kinds of stone to resist the action of frost ; the 

 portion of matter separated from them, and lying in the solution 

 beneath, is to be collected, washed, dried, and weighed ; and the 

 weight indicates the proportion in which the samples tried would 

 suffer by exposure to weather and frost. — Ann. des Mines-, 

 ix. 741. 



7. Economical Method of warming Manufactories^ &c. — Mr. 

 Bewley, of Montraith, Ireland, has contrived a method of warming 

 his cotton-mill by the waste heat of a lime-kiln, apparently in a 

 very effectual manner. The kiln is closed in at the top by a 

 cover of cast-iron, from the middle of which a cast-iron flue 

 proceeds, carrying off the carbonic acid, smoke, ^c. This is sur- 

 rounded by a larger pipe intended for the conveyance of air, 

 which commencing at a brick enclosure surrounding the top of 

 the kiln, continues to the upper part of the building, and has 

 openings from it into the rooms of the mill, for the passage out- 

 wards of the air that has been heated during its ascent through it. 

 Altogether, therefore, it resembles in principle Perkins' stove. 

 The particular advantages mentioned by Mr. Bewley are, that a 

 very cheap kind of fuel may here be used, scarcely fitted indeed 

 for any other purpose, namely, culm, cinders, t^'C, and that the 

 lime produced will in almost all situations pay the expenses, and 

 in many afford a profit. The heat also is a very steady one, and 

 is continued during the night as well as the day, by which changes 

 of temperature, sometimes injurious, are avoided. The work- 



