OBJECTS, PLEASURES, AND ADVANTAGES OP SCIENCE. 



in the 'barometer ia only 28 or 29 inches, mercury being between 13 and 14 times heavier than water, 

 llence, too, the motion of the steam-engine ; the piston of which, until the direct force of steam was applied, 

 used to be pressed downwards by the weight of the atmosphere from above, all air being removed below 

 by filling the cylinder with steam, and then suddenly cooling and converting that steam into water, so as to 

 leave nothing in the space it had occupied. Hence, too, the power which some animals possess of walking 

 along the perpendicular surfaces of walls, and even the ceilings of rooms, by squeezing out the air between 

 the inside of their feet and the wall, and thus being supported by the pressure of the air against the outside 

 of their feet. 



The science of Opt i ft (from the Greek word for teeing), which teaches the nature of light, and of the 

 sensation conveyed by it, presents, of itself, a field of unbounded extent and interest. To it the arts, and 

 the other sciences, owe those most useful instruments which have enabled us at once to examine the 

 minutest parts of the structure of anhnal and vegetable bodies, and to calculate the sire and the motions of 

 the most remote of the heavenly bodies. But as an object of learned curiosity, nothing can be more singular 

 than the fundamental truth discovered by the genius of Newton, that the light, which we call white, 

 is in fact composed of all the colours, blended in certain proportions ; unless, perhaps, it be that astonishing 

 conjecture of his unrivalled sagacity, by which he descried the inflammable nature of the diamond, and its 

 belonging, against all appearance of probability, to the class of oily substances, from having observed, 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, resembling 

 both light and heat, which, by rubbing, is found to be produced in a certain class of bodies, as glass, 

 wai, 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 ia 

 the same matter which, when collected in the clouds, and conveyed from them to the earth, we call 

 lightning, and whose noie, in darting through the air, is thunder. The observation of some movements ill 

 the limbs of a dead frog gave rise to the discovery of Voltaic Electricity, or Galvanism, as it was at first 

 called from the name of the discoverer; and which haa 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 the labour we bestow 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 elaborate experiment and calcu- 

 lation, that we owe our acquaintance with the extraordinary metals potassium and sodium, lighter than 

 water, and more inflammable than phosphorus, which form, when burned by mere exposure to tlie air, two 

 of the salts best known in commerce, aud the principal ingredients in saltpetre and common salt. 



In order to explain the nature and objects of those branches of Natural Science more or less connected 

 witli the mathematics, some details were necessary, as without them it was difficult immediately to perceive 

 their importance, and, as it were, relish the kind of instruction which they afford. But the same course 

 need 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 bodies; the relations of simple substances to heat and 

 to one another, or their combinations together; the composition of those which nature produces in a com- 

 pound state ; and the application of the whole to the arts and manufactures. Some blanches 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 Mechanics aud 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 j 

 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 belongs Natural History, in 

 so far as it describes the habits of animals and plants, and its application to that department of Agriculture 

 which treats of cattle and their management. 



IV. APPLICATION or NATURAL Scizicci TO THE AHIM.VL AND VIGXTABI^ WOBLD. 



BUT, for the purpose of further illustrating the advantages of Philosophy, its tendency to enlarge the mind, 

 M well as to interest it agreeably, and afford pure and solid gratification, a few instances may be given 

 of the singular truths brought to light by the application of Mathematical, Mechanical, and Chemical 

 knowledge to the habits of animals and plants; and some examples may be added of the more ordinary 

 and easy, but scarcely less interesting observations, made upon those habits, without the aid of the 

 profounder sciences. 



\\,- may remember the curve line which mathematicians call a Cycloid. It is the path which auy poiut 



