The reason why so many patents fail. 73 



tion, is very insufficient. One great reason why only 

 a small portion of patents are of practical value ; and 

 so many useless ones are taken out is, that in con- 

 sequence of our so-called "practical" spirit, we over- 

 estimate the power of invention and under-value the 

 discovery of new abstract truths ; because also inven- 

 tion has done so much, we think it will continue to do 

 so, but the latter depends upon a continued supply of 

 discoveries. 



Nearly every manufacturer is aware by painful ex- 

 perience of the great and almost incessant variation 

 that occurs in the quality and properties of the mater- 

 ials used in his trade, and the frequent risk of failure 

 of his process, In the manufacture of iron, for 

 example, the presence of much phosphorus, sulphur, 

 or silicon in the ore is liable to be very detrimental to 

 the quality of the iron produced from it; in the manu- 

 facture of glass, the least quantity of iron in the 

 materials will seriously injure the colour of the product; 

 in the selection of copper for telegraph wire, if it con- 

 tains the least trace of arsenic, the wire will not conduct 

 the electricity properly. The difficulties experienced 

 in procuring suitable materials for a manufacturing 

 process are in some cases very great ; and when they 

 are procured, additional difficulties arise from the in- 

 ability of the manufacturer or his manager to analyse 

 them. 



Every manufacturer is also aware that the difficulties 

 encountered in manufactures are not limited to the 

 substances employed, but extend to all the different 



