INTBODrCTOET.] 



UNDULATORY FORCES. 



commence the study of any of the sections. Some little difficulty, however, may be presented in the first sub- 

 division viz., that which treats on Experimental Philosophy, in connection with the Undulatory Forces ; and we 

 shall, therefore, endeavour to smooth the way of the student by some general remarks on their nature, laws, and 

 correlation. As we shall see in our progress, the term is comparatively new, and has been applied to Heat, Light, 

 <tc. , on account of certain theoretical views which are maintained at the present day. By means of the theory 

 referred to, the various phenomena of each force can be viewed in a definite relation to those of the rest, and thus 

 great assistance is rendered to the philosopher in generalising on, and to the student in acquiring, the facts -which 

 they present to our observation. 



THE PHENOMENA. AND LAWS OF THE UNDULATORY FORCES. 



THE most indifferent observer of natural phenomena cannot fail to notice the variety which presents itself on every 

 hand ; and we can scarcely imagine a more interesting occupation for an intellectual creature, than to trace the causes 

 of those changes which are thus continually afforded us. In no department of Natural Science is there any possibility 

 of disappointment; in fact, wherever we attempt the investigation of those laws which govern Creation, order, 

 beauty, and precision are prominent characteristics. 



It, however, is impossible that we can suddenly appreciate the perfection which Philosophy discloses to us, in all 

 the arrangements and sequences of prime causes, unless we enter into their study with a determination to put aside 

 every preconceived notion, and to be taught by the lessons which are but slowly unfolded to us. To all but the 

 humble philosopher, Nature is a sealed book ; but to those who enter her kingdom as little children, a storehouse of 

 knowledge and enjoyment is at once opened. 



This humility, however, is only arrived at after much experience, because there is an idea entertained by every 

 tyro in Science, that he is at once capable of understanding the assumed simplicity of natural laws. The true man 

 of Science has to arrive at this by slow degrees ; and, after achieving a position which, to ordinary minds, seems to be 

 one of the highest importance, he so far learns his own ignorance as to doubt whether he has attained to any 

 knowledge. In the words of an eminent living philosopher, " I once thought that I knew all that was to be 

 known of Science ; but the longer I live, the less I seem to know of it." 



These remarks are fully borne out by the fact, that all our discoveries of the causes of most of the effects 

 observed in nature, have been arrived at by the most difficult and laborious processes. It matters not what 

 department of Science we choose as illustrative of this truth. In every branch observation has frequently been 

 baffled, the process of induction has been delayed, and the establishment of an adequate theory has been effected 

 only by the most extended investigations, after apparently accurate inductions have undergone the sifting process of 

 many independent and occasionally hostile minds. 



If, however, we study the result of such labours, wo cannot but admire the perseverance which has been 

 employed, and must rejoice that human intellect holds so proud a station as that of being able, to a small extent, to 

 understand those laws which God has impressed on all His works. Even beyond this, we now reap the fruit of the 

 works of those who in former days devoted themselves to investigate some of the most intricate of the operations in 

 nature. The labours of a Newton and a Leibnitz are now the very bases of our national prosperity ; for without the 

 result* which those great men first opened out, our position as a maritime people would yet have to be won. 



In many instances, the most valuable additions to scientific stores have been accidentally met with. We must 

 not, however, forget, that while so-called " accidents" occur to every observer, they are only made use of by those 

 whose minds are prepared to reflect on, and examine, any new appearance which may attract their attention. The 

 discovery of the polarisation of light, and of electricity evolved by chemical action, are instances of the most common 

 occurrences being turned to philosophic purposes. Every one must have observed that the light of the sun produces 

 most beautiful colours when reflected from a thin film of oil floating on water ; but it required the penetrative genius 

 of Newton to explain their cause : and, since his time, the most talented intellects of the day have never ceased to 

 expand the ideas whose germ Sir Isaac first Rave in his experiments with the thin plates of light on the soap-bubble, 

 and those produced between two pieces of glass closely pressed together. 



In reference to processes in various kinds of manufacture, it is often found that great progress has been effected 

 entirely independent of accurate scientific information ; but such progress has been necessarily slow, owing to the want 

 of knowledge on the part of those who had to superintend the operations. At the present time, however, a fresh 

 discovery is scarcely made in any branch of scientific research, before its applications are instantly effected ; and, 

 possibly, the two most remarkable instances on record of this nature, are those of the Electric Telegraph and 

 Photography the two greatest marvels of our age. 



We may, as illustrating this position, adduce the state of the glass manufacture during the Roman era, and 

 that which it occupies at this moment. In the time of Nero a glass vessel cost an almost fabulous price, whilst now 

 the meanest utensil is made of that material This, and many such results, have accrued solely through a knowledge 

 of certain natural laws being first obtained, and afterwards applied by intelligent and scientific manipulators. 



Nearly all the most remarkable and beneficial inventions which have been produced during the last two 

 centuries, have been the result of deep researches into the action of those forces which have been termed imponder- 

 able agents, or, as they are now called, " Undulatory Forces." Thus, in the applications of Heat, Light, Electricity, 

 and Magnetism, we have remarkable illustrations of the value which is involved in the extended study of abstract 

 Science, antecedent to applying the results so obtained in a practical form. By the study of the laws of latent 

 heat, Dr. Black and James Watt have presented us with that mightiest of human contrivances the Steam-Engine. 



Our immense riches in iron and coal were as dross until extensive arrangements were constructed, by means of 

 which intense and long-continued heat could be produced in our furnaces. To the earlier investigators of the laws 

 TOL. I. 



