The following article is extracted from the t)ages of L~.qineering~ Oct. 18, 1878, where it appeared ill consequence of its being a part of a discussion betbre the British Association where the experiments o1~ the electric light made bv the Franklin Institute in 1878 were referred to. It has been republished at this late day in our pages so that the JOURNAL shall include in its records the fullest statement of the condition of the art of electric lighting at the time when the experiments were instituted.
It is probable, at this time, the best adjustment of quantities of light to dimensions of coils and of wire and to the power expended, will give nmximums of light prodnced per horse-power nmch in excess of those established by the committee. But the direction of inquiry and the course of argument in considering the results can never differ from the investigations and tenor of the report which the commitWe and the accompanying paper have established.
"The remarks made by me in the discussion of Mr. Shoolbred's paper on electric lighting, which he presented at the recent meeting of the British Association ibr tt:e Advancement of Science, can be properly supplemented or extended by an inquiry into the relation ()f the expenditure of heat in the produ(',tion of light by means of the burning of coal gas on the one hand or by electrical tbree on the ~ther. These relations can be h)oked upon from several points of view. The first of these would be the purely theoretical one, and i~ based on the absolute heat which would be evolved under the condition of 1)erI~c~ combustion and absolute absorption of heat of coal gas in producing a given light, as coml)m'ed with the heat w]tich represents the same light as derived fi'om the power expended in producing it.
"There is produced the light eii~ct of one stan(lard candle by the eombustion of one-third of a cubic tbot of coal gas eac, h hot,r. That is, this result is that of the tests for qu~tli W of coal gas as established by law, bt,t in practice of gaslighting with the usual itnperfeet burners not much above (if so much as) one-half the quantity of light is, obtained. 3_ccepting tills qtmntlty it (.m be asserted that the heat