6(j ANNUAL OF SCIENTIFIC DISCOVERT. 



'* ' It is also said that an English engineer proposes employing 

 solar heat in generating steam. By using a lens of small diame- 

 ter the sun's rays have been concentrated in a vessel containing 

 water, to such a degree that enough steam luis heen generated to 

 drive a small engine. Increasing the size of the lens will, he con- 

 tends, have the effect of still further intensifying the solar heat, 

 and the power that may be obtained is onl}" to be limited by the 

 dimensions of apparatus employed/ '■ 



PULVERIZED FUEL. 



Mr. James D. Whelpley read a paper before the Massachusetts 

 Institute of Technology, on a new form of furnace for burning 

 solid, but more especially pulverized, fuel, giving the results of 

 trials made by naval engineers appointed by the department; 

 these, though interrnpted by accident, were sufficient to establish 

 the great superiority of dnst coal, reduced to excessive fineness, 

 over solid fuel in the generation of steam. The inventors had 

 found it necessary to apply the principle of the burning glass to 

 the combustion of ores ; in other words, to concentrate heat of 

 reflection and radiation by covering the interior lines of fire-walls 

 so that they should radiate their heat upon t!ie central line or axis 

 of combustion. The practical conclusion is, that radiation, and not 

 convection or conveyance, is the most effective method of impart- 

 ing heat to boilers. 



The experiments show that, with properly constructed and 

 managed furnaces, the poorest, most sulphurous, and earthy va- 

 rieties of waste coal and shales, even those containing only 60 per 

 cent, of carbon, can be burned as thoroughly and completely, 

 after fine pulverization, as the best-selected coals of England or 

 Pennsylvania, and with equally good effects, measured by the 

 quantity of pure carbon contained in them. Solid and dust fuels 

 seemed at first to give the same results, but the effect of j)ulveriza- 

 tion rose gradually to the enormous difference of 44: per cent, over 

 solid fuel, when equal quantities were put in competition. The 

 only explanation of this gain is to be found in the employment of 

 extended radiation from solid particles in place of convection by 

 gases. The efficiency of a mass of particles, as an agent of radia- 

 tion, is inversely as its diameter. The thermotic efficiency of a 

 cubic inch of coal is made 1,000 times greater by subdivision into 

 a thousand parts by pulverization, by the extent of surface thus 

 made an agent of radiation. In addition to minute subdivision of 

 the fuel, ever}" particle should be invested with an atmosphere of 

 oxygen, either in air or a mixture of air and carbonic acid. The 

 proportion of any gas which a sphere or cube of solid matter can 

 condense on its surface is inversely as the diameter of the parti- 

 cle, since this condensation is simpl}^ an affair of surface. In pul- 

 verizing carbon we arrive finally at a size of particle small enough 

 to condense upon its surface all the ox3^gen it requires for the for- 

 mation of carbonic acid. This will be the ideal limit to be at- 

 tained for perfect and instantaneous combustion. 



