mTERCOKN-ECTION OF ITS BRANCHES. 187 



be subjectively so — they cannot have independence as pre- 

 sented to our consciousness ; and this is the only kind of 

 independence with which we are concerned. And here, 

 before leaving these illustrations, and especially this last 

 one, let us not omit to notice how clearly they exhibit that 

 increasingly active co?ise?isus of the sciences which charac- 

 terizes their advancing development. Besides finding that 

 in these later times a discovery in one science commonly 

 causes progress in others ; besides finding that a great part 

 of the questions with which modern science deals are so mix- 

 ed as to require the co-operation of many sciences for their 

 solution ; we find iathis last case that, to make a single good 

 observation in the purest of the natural sciences, requires 

 the combined assistance of half a dozen other sciences. 



Perhaps the clearest comprehension of the interconnect- 

 ed growth of the sciences may be obtained by contemplat- 

 ing that of the arts, to which it is strictly analogous, and 

 with which it is inseparably bound up. Most intelligent 

 persons must have been, at one time or other, struck with 

 the vast array of antecedents pre-supposed by one of our 

 processes of manufacture. Let him trace the production 

 of a printed cotton, and consider all that is implied by it. 

 There are the many successive improvements through 

 which the power-looms reached their present perfection ; 

 there is the steam-engine that drives them, having its long 

 history from Papin downwards ; there are the lathes in 

 which its cylinder was bored, and the string of ancestral 

 lathes from which those lathes proceeded; theie is the 

 steam-hammer under which its crank shaft was welded ; 

 there are the puddling-furnaces, the blast-furnaces, the coal- 

 mines and the iron-mines needful for producing the raw 

 material ; there are the slowly improved appliances by 

 which the factory was built, and lighted, and ventilated ; 

 there are the printing engine, and the die house, and the col* 

 our laboratory with its stock of materials from all parts of 



