28$ Researches upon the Heat developed 



I freely admit, that I have paid very little respect to som*' 

 experiments which have been communicated to me, when 

 I knew that they have been performed in so nealigent sc 

 manner; and certainly I shall never throw awav lime iii 

 endeavouring to build theories on their results. 



In using the apparatus whicli I have described, jt is ne- 

 cessary to have recourse to several precautions. It is easy 

 lo see in the first place, that wiien it is necessary to deter- 

 njine the quantity ol heat developed iti the combustion of 

 any inflammable substance, it is indispensably necessary to 

 arrange matters in such a way as lo make the combustiori 

 complete ; and I am of opinion ihat it may be regarded as 

 coaipkle, when the substance burned no longer leaves any 

 residue, and burns with a bright flame without smoke or 

 smell. 



The least smell, particularly that which is peculiar to the 

 inflan)mable body which we burn, is an infallible indication 

 that the combustion is not perfect. 



It was long before I discovered the method of burriing in 

 a satisfactory manner the very volatile liquids, such as al- 

 cohol and ether; but I finally succeeded, as will presently 

 appear. I have frequently succeeded in burning highly 

 rectified sulphuric ether, without the least smell of ether 

 being perceptible in the room, and it was only under these 

 circumstances that I regarded the experiment as accurate. 



As lo the woods, I discovered a very sin)ple method of 

 burning them without the least appearance of smoke ot 

 smell. I procured from a joiner some chips of wood about 

 six lines broad and one-tenth of a line in thickness; and 

 by holding them between the fingers, or with a pair of 

 pincers, elevated at an angle of 45 degrees, and with their 

 edge in a vertical position, they burned like a taper, and 

 with a very fine flame. 



The piece of wood which is burnt being very thin, and 

 being between two fiat frames which embrace it very closely, 

 is exposed to the action of so strong a heat that it burns 

 completely. If very thick chips are emploved, a part of 

 the charcoal of the wood remains, particularly if it be oak, 

 or any other wood which burns slowly; and in this case 

 the experiments are not good ; but in making use of thin 

 well dried chips, I have discovered that all kinds of wood 

 may be burned completely. 



In burningcandles, tapers, and oils in lamps, the only pre- 

 cautions necessary consist in arranging the wick in such a way 

 as to give out no smoke j then place the flame conveniently 



under 



