1819.] Dr. Henry's Experiments on the Gas from Coal. 33$ 



draw from them; and this 1 should have been very glad if Mr. 

 Meikle had been pleased to undertake. 1 am,' Sir, 



Your most obedient humble tenant, 



P. Keith. 



Article III. 



Experiments on the Gas from Coal, chiefly witli a View to its 

 P tactical Application. " By William Henry, M.D. F.R.S. &c * 



Thk chemical properties and composition of the gas from coal 

 formed a principal object of two different series of experiments, 

 the results of which I laid before the public many years ago. 

 The first of these communications, entitled " Experiments on 

 the Gases obtained by the destructive Distillation of Wood, 

 Peat, Pit-Coal, Oil, Wax, See. with a View to the Theory of 

 their Combustion, when employed as Sources of Artificial 

 Light," appeared in Mr. Nicholson's Philosophical Journal for 

 June, 1805 ;f and the second memoir was published in the 

 Transactions of the Royal Society for 1808. 



By the first train of experiments, I endeavoured to derive, 

 from a careful analysis of the compound combustible gases, a 

 measure of their illuminating power, admitting of more exact 

 appreciation than the optical method of a comparison of sha- 

 dows. The one which 1 was led to propose as the most accurate, 

 and which I still think entitled to preference, was the determi- 

 nation of the quantities of oxygen gas consumed, and of carbonic 

 acid formed, by the combustion of equal measures of the differ- 

 ent inflammable gases ; that gas having the greatest illuminating 

 power, which, in a given volume, condenses the largest quantity 

 of oxygen. The average results of a great variety of experi- 

 ments were comprised in the following table : 



Qxysensras required n . .. 



v j c '. . » Inn Carbonic acid 



Kinds of MS. lo fatiuate !00 , 



measure?. * 



Pure hydrogen 50 — 



Gas from moist charcoal 60 33 



wood (oak) 54 35 



dried peat 08 43 



catinel coal 170' 100 



ip-dil 190 124 



wax 220 137 



defiant gas 284 179 



* From ih- IV'cmo'rs of V.c Literal v nnd Pi.iiosopVca' Society :if Mandi osier 

 Till. iii. Second S< rj< s. 



"t Bvo. Series, vol. tfi. p. fi . 



