PHYSICAL SCIENCES TO SCIENCE IN GENERAL. 229 



above great model, especially optics, electricity, and niaguetisin. Tbe ex- 

 perimental sciences have the advantage over the rest, tliat they can at 

 will vary the conditions under which a result takes place, and may thus 

 confine themselves to the observation of comparatively few character- 

 istic cases in order to determine the law. Its correctness must, of 

 course, be verified in more complicated cases. Thus the physical sciences 

 have advanced with comparative ra[)idity after the correct methods had 

 once been determined. They have not only enabled us to look back into 

 the distant past when the cosmical nebulae were consolidated to stars 

 and became incandescent by the power of their aggregation ; not oidy 

 to investigate the chemical constituents of the solar atmosphere — the 

 chemistry of the most distant fixed stars will probably soon become 

 known also* — but they have taught us to avail ourselves of the forces 

 of nature for our own benefit. 



From what has been said, it is sufficiently evident how different the 

 mental labor is in the two classes of sciences. The mathematician needs 

 no memory at all for individual facts, and the physicist but little. Sup- 

 positions based on the recollection of similar cases may bo useful in 

 indicating the right direction, but they become valuable only when they 

 have led to a precise and marked law. There is no doubt that we have 

 to do in nature with unvarying laws. We must, therefore, work on 

 until we have discovered them. We must not rest until we have accom- 

 plished that; for it is then only that our knowledge obtains its triumphs 

 over time and space, and over the forces of nature. 



The solid work of conscious argument requires great perseverance and 

 care ; it is generally slow, and is but rarely advanced by flashes of 

 genius. We find in it little of that readiness with which the memory of 

 the historian or philologer recalls past experiences. It is, indeed, the 

 essential condition of methodical progress of thought that the mind 

 must remain concentrated upon one point, undisturbed by side issues, 

 by wishes or hopes, and proceed only according to its own will and 

 determination. The celebrated logician, Stuart Mill, asserts as his con- 

 viction that the inductive sciences have done more in modern times for 

 the progress of logical methods than philosophy itself. One great cause 

 of this may be, that in no department of knowledge is a mistake of 

 reasoning detected so easily by the erroneousness of the result as in 

 these sciences, where we can most readily compare the results of our 

 reflsoning directly with the actual facts. 



Although I have asserted that the natural sciences, and especially 

 their mathematical branches, have come nearer the accomplishment of 

 their scientific mission than the other sciences, I do not wish to be charged 

 with underrating the latter. If the natural sciences hav^e attained 



* Most interesting discoveries have already been made. They are found in the work 

 of W. Huggins and W. A. Miller, published April, 1804, in which the analysis of Alde- 

 haran and a Orion is given, and proof furnished that certain nebuhe are incandescen 

 globes of gas. 



