1870.] On Practical Scientific Instruction. 217 



principles, and facts ; an art consists of technical directions and 

 manipulations ; and the latter is in all cases based upon the former, 

 although in some instances the connection between them may not 

 be well understood. Thus we have the science of electricity, and 

 the arts of electric telegraphy and of electro-plating based upon it ; 

 and the sciences of heat and chemistry, with the arts of ventilation, 

 photography, soap-making, iron-smelting, &c, depending upon them. 

 In science, the great aim is truth and accuracy ; in art and manu- 

 facture the chief object is to produce the best practical result at the 

 lowest possible cost. 



Every special art or manufacture consists essentially of some 

 particular process, or series of operations, generally reduced to the 

 greatest degree of simplicity in order to lessen the cost of produc- 

 tion. In each different trade or manufacture a knowledge of the 

 process is implicitly embodied in a number of instructions and details 

 with which each workman is supposed to be fully and familiarly 

 acquainted. Each manufacture is an art, the methods of which are 

 based upon definite scientific facts and principles. What an English 

 manufacturer generally expects of a workman is not a knowledge of 

 the science or sciences upon which his manufacture is based, but a 

 knowledge of those empirical methods, and ready practical expe- 

 rience in their use. In accordance with this expectation an English 

 workman usually possesses a knowledge of the empirical methods or 

 directions of his trade, but rarely understands their scientific basis : 

 for example, a brass dipper knows that the methods for cleaning a 

 figured piece of brass is to dip it into aqua-fortis, but does not under- 

 stand the general chemical relations of acids and metals, or the spe- 

 cial chemical effects of aqua-fortis on brass. The empirical methods 

 of his trade, without which a workman could not work at all, have 

 of necessity always been taught him, but a knowledge of their sci- 

 entific basis, which would enable him to work to the greatest advan- 

 tage, has been greatly neglected. 



In some cases this blind following of methods, sometimes called 

 " the rule of thumb," is sufficient, though very imperfectly so, for 

 the manufacturer's purpose, which is to make the production of his 

 goods as much as possible a matter of routine ; but in most trades 

 the following of empirical rules alone very frequently does not lead 

 to the desired perfect result, the articles produced are imperfect, 

 and then it is that a knowledge of science is necessary to enable the 

 manufacturer or his men to avert or correct the evil. In such cases 

 under present arrangements the manufacturer frequently finds fault 

 with the materials supplied to him, or he sometimes applies to a 

 scientific man for advice. In many cases, also, the following of 

 those rules does not lead in the test way to the desired result, the 

 materials, time, or labour are not used in the most advantageous 

 manner, and the cost of the finished article is thereby made too great. 



