D'ALEMBERT. 489 



more, than to find that the colour of white is a mixture of all 

 others that red, and blue, and green, and all the rest, merely 

 by being blended in certain proportions, form what we had 

 fancied rather to be no colour at all, than all colours together ? 

 Chemistry is not behind in its wonders. That the diamond 

 should be made of the same material with coal ; that water 

 should be chiefly composed of an inflammable substance ; 

 that acids should be, for the most part, formed of different 

 kinds of air, and that one of those acids, whose strength can 

 dissolve almost any of the metals, should consist of the self- 

 same ingredients with the common air we breathe ; that salts 

 should be of a metallic nature, and composed, in a great part, 

 of metals, fluid like quicksilver, but lighter than water, and 

 which, without any heating, take fire upon being exposed to 

 the air, and by burning form the substance so abounding in 

 saltpetre and in the ashes of burnt wood ; these, surely, are 

 things to excite the wonder of any reflecting mind, nay, of 

 any one but little accustomed to reflect. And yet these are 

 trifling when compared to the prodigies which astronomy 

 opens to our view: the enormous masses of the heavenly 

 bodies; their immense distances; their countless numbers, 

 and their motions, whose swiftness mocks the uttermost 

 efforts of the imagination. 



Akin to this pleasure of contemplating new and extra- 

 ordinary truths, is the gratification of a more learned curiosity, 

 by tracing resemblances and relations between things which, 

 to common apprehension, seem widely different. Mathe- 

 matical science, to thinking minds, affords this pleasure in a 

 high degree. It is agreeable to know that the three angles of 

 every triangle, whatever be its size, howsoever its sides may 

 be inclined to each other, are always of necessity, when taken 

 together, the same in amount : that any regular kind of figure 

 whatever, upon the one side of a right-angled triangle, is 

 equal to the two figures of the same kind upon the two other 

 sides, whatever be the size of the triangle : that the properties 

 of an oval curve are extremely similar to those of a curve, 

 which appears the least like it of any, consisting of two 

 branches of infinite extent, with their backs turned to each 

 other. To trace such unexpected resemblances is, indeed, the 



