48 The laws of matter are the same for all men. 



stock of positive knowledge, but from additions made 

 to it. Demonstrable truth is imperishable. It is true 

 that many theories have been invented and enter- 

 tained for a while in the minds of scientific men, 

 and have then passed away, but we must remember 

 that these are only the scaffolding of science, and no 

 part of its real fabric. They consist of ideas which, 

 whilst they assist us in understanding science, and 

 in making discoveries, form no real part of our 

 positive knowledge. 



Other persons seem to think that the laws of 

 matter are different in the laboratory from what they 

 are in the workshop ; that the principles which 

 regulate a scientific experiment are different from 

 those which govern a large manufacturing process ; 

 but this is a wrong idea. The laws of matter are 

 universal, substances have nearly the same proper- 

 ties in all places and in the hands of all men ; water 

 boils at the same temperature whether in the retort 

 of a chemist, the saucepan of a kitchenmaid, or 

 the pan of a soap-boiler ; iron wire is as readily 

 deprived of its rust in a chemist's acid bottle as in a 

 wire-drawer's pickling tub ; a piece of phosphorus 

 will as readily ignite in the hands of a chemist as in 

 those of a match maker ; a galvanic battery yields 

 the same quantity of electricity whether it be in the 

 hands of an experimentalist or in those of a working 

 electro-plater. 



It is true that many things which have appeared 

 very promising in theory or in experiment, have 



