LECTURES. 101 



(16.) It sliould be recollected that laws of nature are contingent 

 truths, or such as might be different from what they are for anything 

 we know — that they can only be established by induction from facts 

 of experience — that they admit of no other proof than the a posteriori 

 one of the exact agreement of all the deductions from them witli the 

 actual phenomena of nature, and that no other reason can be assigned 

 for their existence than the will of the Creator. 



(17.) It should also not be forgotten that the great test of tlie per- 

 fection of any branch of science, and of the truth of its laws, is the power 

 it gives us of predicting events when the circumstances are known. 



(18.) Importance of mathematics in the study of physical science, 

 principally used in the process of deduction. 



It is the great instrument of all exact enquiry relative to time, 

 space, order, number, &c. And as the material universe exists 

 in space, and consists of measureable parts, and its operations are 

 produced in time and by degrees, the abstract truths of mathematics 

 are applicable by analogy to the development of those of external 

 nature. 



(19.) Importance of experimental illustrations in teaching physical 

 science. 



They serve to give a clear idea of the phenomena, and make an in- 

 delible impression on the mind. 



(20.) The ultimate tendency of the study of the physical sciences 

 is the improvement of the intellectual, moral, and physical condition 

 of our species. It habituates the mind to the contemplation and dis- 

 covery of truth. It unfolds the magnificence, the order, and the 

 beauty of the material universe, and affords most striking proofs of 

 the beneficence, the wisdom and power of the Creator. It enables 

 man to control the operations of nature, and to subject them to his 

 use. 



(21.) We propose to treat of the general subject of natural phi- 

 losophy in order as follows : 



1. Somatology. 



2. Mechanics, (Rational and Physical,) including Statics and Dy- 

 namics. 



3. Hydrostatics and Hydrodynamics. 



4. Pneumatics, including Aerostatics and Aerodynamics. 



5. Heat, including the Steam Engine. 



6. Sound, including the doctrine of vibrations. 



7. Electricity and Magnetism, including Galvanism, Electro-Mag- 

 netism, &c. 



8. Light and Radiant Heat. 



9. Meteorology. 



Difficulty of giving a clear idea to these different branches ; to un- 

 derstand any one of them requires some knowledge of all the others. 



