L. MECHANICS AND ENGINEERING. 485 



is necessary, and to a much greater advantage, as it passes 

 directly through the coal instead of playing on the top ; and 

 the combustion is much more uniform and thorough. At 

 intervals the bar is turned partly round, and a clear surface 

 free from slag and scale is presented to the fuel. The ashes 

 which fall through the perforations of the grate can be push- 

 ed out into the ash-pit, thus avoiding the necessity of raking 

 down. 



Another advantage claimed for this grate is that a larger 

 charge of coal can be put into the furnace than usual, thus 

 avoiding the necessity of a frequent opening of the front. 

 In an experiment by the Paris Gas Company with these 

 bars, the fuel used was an agglomerated coke dust which 

 could not be used in ordinary furnaces and which resulted 

 in complete success, and by which it was claimed that a 

 saving of 26 per cent, was made. 3 A, April 24, 520. 



CORK AS A XOX-COXDUCTOR OF HEAT. 



Experiments conducted at several important works in 

 France, during a number of months, are declared to have 

 established the fact that cork is entitled to the first rank as 

 a non-conducting substance well adapted for the purposes 

 of practice. In the account from which our information is 

 derived, it is said that after eighteen months of service upon 

 the steam-pipes of sundry establishments, the cork remained 

 intact, and had suffered no practical deterioration of quality. 

 Although the durability of this substance had been proved 

 before by the buoys which are subjected to the severe test 

 of a partial immersion in water and exposure to weather, 

 its ability to withstand such high temperatures as those of 

 steam-heated surfaces required experimental demonstration. 

 This point, according to our authority, has been satisfactorily 

 settled. In addition to its durability, its lightness, the readi- 

 ness with which it yields so as to surround the cylinders or 

 pipes, the facility with which it can be taken down and put 

 in place again whenever inspection or repairs of boilers and 

 pipes require it, and above all its eminent non-conducting 

 powers, entitle it to the first rank as a heat-saving lining to 

 steam-pipes and for related applications. The engineers of 

 the French Navy, after a lengthy examination of its merits, 

 have, according to accounts, given it their formal approval in 



