26 OBJECTS, ADVANTAGES, AND 



unrivalled sagacity, by which he descried the inflammable nature o 

 the diamond, and its belonging, against all appearance of probability, 

 to the class of oily substances, by observing that it stood among them, 

 and far removed from all crystals, in the degree of its action upon 

 light ; a conjecture turned into certainty by discoveries made a century 

 afterwards. 



To a man who, for original genius and strong natural sense, is not 

 unworthy of being named after this illustrious sage, we owe the greater 

 part of Electrical science. It treats of the peculiar substance, resem- 

 bling .oth light and heat, which, by rubbing, is found to be produced in 

 a certain class of bodies, as glass, wax, silk, amber ; and to be conveyed 

 easily or conducted through others, as wood, metals, water ; and it 

 has received the name of Electricity from the Greek word for amber. 

 Dr. Franklin discovered that this is the same matter which, when col- 

 lected in the clouds, and conveyed from them to the earth, we call 

 lightning, and whose noise, in darting through the air, is thunder. The 

 observation of some movements in the limbs of a dead frog gave rise 

 to the discovery of Animal Electricity or Galvanism, as it was at first 

 called from the name of the discoverer ; and which has of late years 

 given birth to improvements that have changed the face of chemical 

 philosophy ; affording a new proof how few there are of the processes 

 of nature, incapable of repaying our labour, bestowed in patiently and 

 diligently examining them. It is to the results of the remark accidentally 

 made upon the twitching in the frog's leg, not, however, hastily dismissed 

 and forgotten, but treasured up and pursued through many an elabo- 

 rate experiment and calculation, that we owe our acquaintance with the 

 extraordinary metal, liquid like mercury, lighter than water, and more 

 inflammable than phosphorus, which forms when it burns, by mere ex- 

 posure to the air, one of the salts best known in commerce, and the 

 principal ingredient in saltpetre. 



In order to explain the nature and objects of those branches of Na- 

 tural Science more or less connected with the mathematics, some details 

 were necessary, as without them it was difficult at once to perceive 

 their importance, and, as it were, relish the kind of instruction which 

 they afford. But the same course needs not be pursued with respect to 

 the other branches. The value and the interest of Chemistry is at 

 once perceived, when it is known to teach the nature of all substances, 

 the relations of simple substances to heat and to one another, or their 

 combinations together ; the composition of those which nature pro- 

 duces in a compound state, and the application of the whole to the arts 

 and manufactures. Some branches of philosophy, again, are chiefly 

 useful and interesting to particular classes, as surgeons and physicians. 

 Others are easily understood by a knowledge of the principles of Me- 

 chanics and Chemistry, of which they are applications and examples ; 

 as those which teach the structure of the earth and the changes it has 

 undergone ; the motions of the muscles, and the structure of the parts 

 of animals ; the qualities of animal and vegetable substances ; and that 

 department of Agriculture which treats of soils, manure, and machinery. 

 Other branches are only collections of facts, highly curious and useful 

 indeed, but which any one who reads or listens, perceives as clearly, 

 and comprehends as readily, as the professed student. To this class 



