421 

 MISCELLANEOUS INTELLIGENCE. 



§ I. Mechanical Science. 



\. M. Brard^s Test of the Action of Frost and fVeatheron Building 

 Materials. — Some years since M. Brard devised a process by which 

 a dej^ree of knowledge was suppHed relative to the property of 

 building stone to resist the action of frost.* This process has been 

 minutely investigated in France, and, with certain precautions, found 

 highly useful. The following is a set of practical directions, which 

 has been drawn up for the purpose of being placed in the hands of 

 architects and workmen. 



i. Specimens of the stone are to be taken from the various doubt- 

 ful places in the quarry, i. e. from places where the colour, grain, 

 and aspect vary. 



ii. These are to be cut or sawn into cubes of two inches in the 

 side, with sharp angles : pieces broken off are not fit for ti-ial, as 

 they may be injured by the force of the blows applied, and so give 

 indications of weakness not belonging to the stone. 



iii. Each specimen is to be numbered, or marked, with China ink, 

 or by a steel point ; and notes relative to the place from which each 

 cube came are to be taken. 



iv. A quantity of water, sufficient for all the specimens, is to be 

 saturated at common temperatures, with sulphate of soda, for which 

 purpose rather more than the water will dissolve should be left in 

 the vessel an hour or two after it has been thrown in. 



V. This solution is to be heated in a convenient vessel until it 

 boils freely ; when, without removing the vessel from the fire, all 

 the specimens are to be introduced, and entirely submerged. 



vi. The boiling is then to be continued for half an hour, and on 

 no account for a longer time ; or effects too strong in their kind 

 will be obtained. 



vii. The specimens are then to be taken out, and suspended by 

 thread or string, so as to touch nothing else. Beneath each is to 

 be placed a clean vessel, containing some of the clear liquor in 

 which the cubes have been boiled. 



viii. If the weather be not too damp or cold, the cubes will be 

 found twenty-four hours afterwards covered with small white saline 

 needles, similar in appearance to the crystals of saltpetre, and other 

 salts occurring upon walls. The cubes are then to be dipped in 

 the portions of solution respectively between each, so as to destroy 

 these crystalline appearances. This is to be repeated each time 

 the crystals are well formed ; they will usually be found larger and 

 more abundant after a night than in the course of a day : the trial 

 may be conducted with advantage in a close apartment or a cellar. 



ix. If the stone tried can resist frost, this operation will remove 

 nothing from it, and there will be found neither grains, nor scales, 

 * See Quarterly Journal, xvii. 148. 



