106 The Rev J. B. Harbord on the Conic Theory of Heat, 



coffee, which coincides very nearly with that employed in making 

 the mixture. The tint of the fluid in the large tube and the in- 

 crease in the bulk of the solid matter are also of use in arriving 

 at a correct estimate. After the performance of a few experi- 

 ments with mixtures of coffee and chicory in different propor- 

 tions, a degree of expertness is obtained which enables the ope- 

 rator to form an accurate estimate of the amount of each ingre- 

 dient in any sample that may be submitted for his examination. 



Not only may coffee be thus to a great extent separated from 

 any chicory with which it is mingled, but nearly all the other 

 substances used for the purposes of adulteration, as exhausted 

 coffee-grounds, wheat, &c, also subside rapidly with the chicory 

 and collect in the small tube. If it is desired to determine the 

 character of the matter that precipitates quickly we must resort 

 to the microscope, when, by the nature of the cells and other struc- 

 tures found, we can soon decide upon the true character of the 

 foreign substances. The presence of chicory is readily and sa- 

 tisfactorily proved ; and if peas, beans, &c. are present, they may 

 be easily distinguished by the peculiarities of the starch-cells of 

 each. Such microscopic examinations are greatly facilitated by 

 the use of the tubes I have described ; for when the subsidence 

 is complete, and we have read off the proportion of adulteration, 

 it only remains to remove the cork gently from the small tube 

 and allow a little of the lower portion of the sediment which 

 contains the foreign matters to escape into a shallow dish, whence 

 particles may be transferred to the microscope-slide ; and if it is 

 necessary, we may in this manner examine layer after layer of 

 the deposit. 



In the hope that the above communication may be found 

 worthy of a place in your valuable Journal, 

 I am, Gentlemen, 



Yours very respectfully, 



John C. Draper. 



XIII. The Conic Theory of Heat, in connexion chiefly with the Me- 

 tamorphosis of Matter. By the Rev. J. B. Harbord, M.A* 



PROFESSOR TYNDALL remarks that "the ideas of the 

 most well-informed philosophers are as yet uncertain re- 

 garding the exact nature of the motion of heat." The following 

 idea I have not yet seen advanced ; and as it is founded on the 

 analogy of nature, and serves to explain and classify the various 

 phenomena in this branch of physics, it may not be unworthy 

 the consideration of the scientific world. 



* Communicated by the Author. 



