Biographical Memoir of the late Dr Turner. 237 



tine,"* — an interesting mineral previously known to consist of 

 sulphate of strontia and sulphate of baryta. Dr Turner shew- 

 ed that the crystallized variety of it consists almost entirely of 

 these two sulphates in such proportion to one another that the 

 mineral forms a definite compound, in which the strontitic 

 salt is to the barytic in the ratio of five atoms to one, — thus add- 

 ing one more to the instances previously ascertained, and now 

 known to be very numerous, which tend to shew that crystal- 

 line minerals, however composite they may be, consist essen- 

 tially of similar compounds united in atomic proportions as ex- 

 actly as the constituents of the common earthy, alkaline, and 

 metallic salts. 



His next investigation was one in which I had the pleasure of 

 being his coadjutor. In the autumn of 1824, at the request of 

 tiie Edinburgh Oil-Gas Company, one of the many joint-stock 

 companies that sprung up in the calamitously speculative years 

 of 1824 and 1825, we undertook a conjunct inquiry into nume- 

 rous ill-ascertained points respecting the manufacture, illumi- 

 nating power, and modes of burning, oil and coal gases. And 

 the first result of this inquiry was a paper, published in the spring 

 of 1825, " On the Construction of Oil and Coal Gas Burners, 

 and the circumstances that influence the light emitted by the 

 gases during their combustion ; with some observations on their 

 relative illuminating power, and on the different modes of as- 

 certaining it.'M- The objects of this paper are to show, that the 

 economical combustion of the illuminating gases depends on a 

 single principle being attended to in every part of the construc- 

 tion of gas-burners, namely, that the gases shall be consumed 

 not more vividly than is just sufficient for their complete com- 

 bustion, — to fix the several points in the construction of burners 

 which are necessary for securing that condition, — to reconcile 

 the conflicting statements of prior experimentalists regardino- the 

 relative illuminating power of the gases with a view to settle what 

 that relative power really is, — and, among other incidental objects, 

 to prove that the late Professor Leslie was wrong in maintaining 

 that his photometer was exempt from the influence of non-lumi- 

 nous heat, or was applicable to the measurement of diflTerentlyr 



• Edin. Phil. Journal, xi. 324, 1824. f Ibid. xiv. I. 



