VOL. XLV.] PHILOSOPHICAL TRANSACTIONS. 55g 



distance of above 120 feet, and silver at 50. The theory which led him to this 

 discovery, is founded on 2 important remarks, the one that the heat is not pro- 

 portional to the quantity of light, and the other that the rays do not come pa- 

 rallel from the sun. The first of these, which appears to be a paradox, is never- 

 theless a truth, of which we may easily satisfy ourselves, by reflecting that heat 

 propagates itself even within bodies ; and that when we heat at the same time a 

 large superficies, the firing is much quicker than when we only heat a small 

 portion of the same. ^ 



Jin Essay on Quantity : occasioned by reading a Treatise, in which Simple and 

 Compound Ratios are applied to Virtue and Merit. By the Rev. Mr. Reid. 

 Communicated in a Letter from the Rev. Henry Miles, D.D., F.R.S. N" 

 489, p. 505. 



Since it is thought that mathematical demonstration harries a peculiar evidence 

 along with it, which leaves no room for further dispute, it may be of some use, 

 or entertainment at least, to inquire to what subjects this kind of proof may be 

 applied. 



Mathematics contain properly the doctrine of measure ; and the object of 

 this scienge is commonly said to be quantity: therefore quantity ought to be de- 

 fined, what may be measured. Those who have defined quantity to be whatever 

 is capable of more or less, have given too wide a notion of it, which it is appre- 

 hended has led some persons to apply mathematical reasoning to subjects that do 

 not admit of it. Pain and pleasure admit of various degrees, but who can pre- 

 tend to measure them ? 



Whatever has quantity, or is measurable, must be made up of parts, which 

 bear proportion to each other, and to the whole ; so that it may be increased by 

 addition of like parts, and diminished by subtraction, may be multiplied and di- 

 vided, and in short, may bear any proportion to another quantity of the same 

 kind, that one line or number can bear to another. That this is essential to all 



volumes of the Royal Academy of Sciences, in 4 vols. 4to. And a general analysis of his works and 

 life in the History of the Academy for the year 1788. An account of his life and writings has also 

 been published separately by M. Cuvier. 



It must not be dissembled however that the natural history of the Count de BufFon, though often 

 distinguished by peculiar eloquence, is of too diffuse and rambling a cast to be considered as a proper 

 model of good writing. His theories are bold and ingenious, but at the same time highly absurd. In 

 his history of quadnipeds he seems to take a particular delight in railing at methodical distribution and 

 minute exactness of description, and affects to be particularly severe against the arrangements of Lin- 

 neus. The work is in reality much more valuable for the anatomical descriptions of Daubenton an- 

 nexed to each article than for the declamatory harangues of the Count de BufFon himself, who seemi 

 not to have perceived, that a natural history conducted on his own plan and principles, must inevi- 

 tably have sunk under its own weight. 



