Mechanical Invention.'— Dutch Proce/s .for making Turnfol blue. 311 



cannot fubmit to the fevere difcipline of feeing his plans reverfed, and his hopes repeatedly 

 deferred — if unfuccefsful experiment fhould produce anguifli without affording inflruc- 

 tion, what will then remain for him to do ? — Will he embitter his life by directing his 

 inceflant efforts, his powers and refources, to a fafcinating objeft, in which his diflicul- 

 ties daily increafe j or, will he make that ftrong exertion of candour and fortitude, which 

 will lead him to abandon it at once? 



Thefe are the inevitable (lages of operation, through which every inventor in mechanics 

 muft pafs. To the mere habit of viewing objefts in new lights, the habit which leads ttJ 

 the outline of invention, he mull add the power of difpoling his notions in the form of 

 an individual engine or inflrument ; and he mufl himfelf become a workman, capable of 

 difcerning the means by which his ideas may become realized in the proper materials. It 

 may perhaps feem as if I had felefted an inflance of difficulty, and indulged my imagina- 

 tion in a fketch of obflacles feldom likely to be met with. This, however, is far from 

 being the cafe. Nothing feems more fimple and eafy at firfl fight, than to make an 

 engine to cut notches in a piece of fteel ; and a very ingenious perfon, in the work above 

 referred to, has accordingly given an accurate defign of an engine for that purpofe, which 

 no doubt he thinks mufl fucceed. But manufafturers well know the value of fuch an 

 engine, and have long ago attempted to make it by that 3S\A various other methods without 

 fuccefs. That engine in particular, promifmg as it appears, is utterly incapable of work- 

 ing, for feveral reafons, fcarcely to be difcovered but by practical men, but which cannot 

 with fufficient brevity be here detailed. And with regard to general obflacles in the detail 

 of inventions, I am fo far from magnifying them, that I am warranted by much ex- 

 perience, as well on my own behalf, as that of others whofe plans and operations have 

 come before me, to affirm, that no mechanical invention really new was ever brought to 

 its cpmplete or perfe£l ftate, at fo fmall a charge as three times the coft of the finifhed 

 engine, cxclufive of the incalculable labour of the contriver. 



VII. 



The Dutch Procefs for making the Blue dijiinguijhed by the Name of Turnfol *. 



i" ^ ICHEN, Archil, or in cafe this lad caanot be obtained, the greater mofs of the oak, 

 is dried, cleaned, and pulverized in a mill, refembling the oil mill, and then lifted through 

 a brafs wire fieve, the interftices of which do not exceed one millimetre in width (i -250th 

 of an inch). The fitted powder is then thrown into a trough, and mixed with an alkali 

 called vedas, which is nothing elfe but the cendres gravelees in powder. The proportioij 

 is one part by weight 0/ the alkali, to two parts of the pulverized vegetable. This mix* 

 tare Is moiflened with a fmall quantity of human urine ; the urine of other animals 

 does not contain a fufficient quantity of ammoniac. The mixture ferments, and is kept 

 molll by fucceffive additions of urine. As foon as the materials have become red, they 

 are transferred into another trough, where they are again moiflened with urine, and ftirred 

 ■to renew the fermentation. Some days afterwards the pafle acqulrcis a blue colour, iq 

 which ftate it is carefully mixed with one third of excellent pot-afh well powdered ; and 



* Sfom the Journal du Commerce, copied in the Decade ^'hilof, &c. No. 57. 



Sf 2 with 



