312 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



requested that a commission bo formed to report on the value of this dis- 

 coveA-y. 



M. Simon, commissioned to bring from China to France the best breed of 

 silk-worms, has sent home a box of eggs to be distributed. Some of these 

 are now being experimented upon at the Imperial farm at Vincennes, 



Fuel. 



Mr. J. A. Miller made some remarks preliminary to the regular discus- 

 sion, on the economical use of fuel. The subject of combustion was second 

 to no other, because it was the mainspring of both animal and mechanical 

 power, when such power is derived from heat. It is admitted that the 

 principles governing combustion are understood by scientific men; at the 

 same time it will not be denied that the proper application of these princi- 

 pies is seldom made. Coal is the source of most of the power used in 

 manufactures and locomotion as well as our chief defense against cold. 

 We should always aim to produce the best results with a given amount of 

 material, yet in no department of the useful arts is waste so disastrous as 

 in combustion. Nearly all other waste products are or can be utilized, but 

 the miconsumed gases when they escape from the chimney are beyond the 

 reach of man. The annual consumption of coal in this country is more 

 than 15,000,000 tons, which, at an average of $5 per ton, is worth $75,- 

 000,000. If, of this amount, 20 per cent, can be saved, the sum added to 

 the wealth of the country is $15,000,000— -the interest at 6 per cent, on a 

 capital of $250,000,000. 



The resultants of the perfect combustion of carbon and hydrcgen by 

 combining with the oxygen of the air are carbonic acid and water. Per- 

 fect combustion can onlj' be obtained by insunng to the fuel a full supply 

 cf oxygen, and the most economical use of the heat is made when only the 

 amount required foi' draft escapes from the chimney. The speaker illus- 

 trated by diagrams some improvements he had introduced for economizing 

 the heat under boilers, relating to the size and form of the furnace, grate 

 bars, and bridges — the latter, instead of allowing the heat to pass ever 

 them, were brought into contact with the boiler, and contained a number 

 of openings, having a slight descent from the front to the back ; there 

 should be at least two of these bridges under an ordinary horizontal boiler. 

 The object of these bridges, designated as lungs, is to facilitate perfect 

 combustion, to abstract the heat from the passing gaseous products, and to 

 give it to the boiler by conduction through the parts in contact and by 

 radiation. Mr. Miller was convinced that in the few furnaces built on this 

 plan there was a saving of heat, but he was not then prepared to furnish 

 any comparative statements. According to experiments made in England, 

 in regard to the regulation of the admission of air to feed the fire, it had 

 been shoAvn that there was a saving of about three per cent, of fuel by the 

 use of self-regulating dampers. 



Mr. T. D. Stetson said he believed most of the automatic arrangements 

 for regulating the draft und(u- boilers have been abandoned. Tliere is, ^ 

 doul)tless, in the ordinary construction of furnaces, much heat wasted. We 

 know that, in theory, the greatest possible evaporation of water, by a given 



