96 ANNUAL OF SCIENTIFIC DISCOVERY. 



France, I believe, this plan is rendered compulsory by the govern- 

 ment, and it would be well were it generally adopted in tin's country 

 voluntarily. Weak places in the plates may pass undetected, even 

 on careful examination, while some parts may be inaccessible and 

 concealed from view ; but the hydraulic test is sure to detect and ex- 

 pose them all. 



" Mr. Muntz, a steam-user in Birmingham, states that he has for 

 years adopted, with advantage, the plan of an annual hydraulic boiler 

 test, and considers it a duty he owes to his workmen in consideration 

 of their safety. The application of the hydraulic test is so simple, 

 and the pump required so small, that each steam-user could provide 

 himself with one at a very little expense, or some parties might find 

 it worth their while to take up the proving of boilers by water pres- 

 sure as an itinerant specialty of engineeriag practice." 



ADAMAS. 



This name is given in England to a preparation of the silicate of 

 magnesia, calcined, moulded, and baked to any required shape, and 

 which for the last few years has been used as a substitute for metal in 

 the manufacture of gas-burners. More recently, however, it has been 

 applied with great success for machine bearings, and for steam and 

 water cocks. The London Artisan states that a steel spindle has 

 been run in an adamas bearing for one hundred entire days consecu- 

 tively, at a speed of about fifteen hundred revolutions per minute, 

 yet neither the spindle nor the bearing showed the slightest appear- 

 ance of wear. It also states that at a large London foundry adamas 

 is used as a fan-bearing in place of a Babbitt's patent white metal 

 bearing, brass having been previously proved to be quite inapplica- 

 ble, owing to the great friction and resulting heat ; and, although the 

 shaft makes nearly one thousand revolutions per minute, it is found 

 that the adamas bearing remains quite cool, requires oiling but once 

 a day, and shows no appreciable signs of wear. In the position in 

 question the life of a Babbitt's bearing is five weeks, and it is confi- 

 dently believed that the adamas will last far more than as many 

 months. 



MICA AND ITS USES. 



Hitherto the use of mica has been limited mainly to the construc- 

 tion of stove and furnace doors, lamp chimneys, lanterns, and a few 

 other industrial applications. Recently, however, a new field has been 

 in the process of opening up by the endeavor to apply mica, previ- 

 ously colored or metallized, to the decoration of churches, rooms, shops, 

 frames, and other ornamental and useful purposes. The mica, from 

 its unalterable nature, preserves the gilding, silvering, or coloring 

 from deterioration, and from its diaphaneity the articles so treated 

 will preserve all their brilliancy. They are further preserved in a 

 state of perfect cleanliness from the action of smoke, dust, or marks 

 of insects, which may all be removed by washing. 



Mica is prepared by Mr. Murray, of Paris, for ornamental purposes 

 as follows : It is first cut to the desired thickness, then coated with 

 a thin layer of fresh isinglass diluted in water, and the gold or other 



