THE POSSESSION OF SCIENTIFIC KNOWLEDGE. 33 



complished by the application of pure science. Guinancl the 

 artizan, and Fraunhofer the optician, both of whom must have 

 depended for success, as it would appear, on circumstances 

 in the production of flint-glass, which can very rarely happen, 

 or which can produce but a very small quantity of perfect 

 glass, when a very large one is formed of that substance, in its 

 ordinary state, succeeded in manufacturing only a small stock 

 of the material of which they were in search. The mere manu- 

 facturer, upon the large scale, unenlightened by chemical 

 knowledge, could never have arrived at a competent insight 

 into the causes which produce striae, and which apparently 

 must continue to produce them, in flint-glass. The chemist 

 alone could have devised and executed the production of a 

 new kind of glass, the constitution of which, as a chemical 

 combination, will enable the manufacturer partly to avoid the 

 causes of striae, and partly to remove them when formed. 



The utility of imparting a knowledge of Chemistry and 

 Natural Philosophy to youth, when destined to take an ac- 

 tive share in manufacturing business, may perhaps appear in 

 a stronger light, from the details just given, than from any 

 others which I have yet offered. Mr. Faraday has described 

 the process by which he has obtained a homogeneous glass, 

 with the utmost clearness and perspicuity; he has enabled 

 any other person, who shall accurately and minutely follow 

 his instructions, to do what has been done at the Royal In- 

 stitution, without incurring the laborious prefatory experiments 

 and investigations which the "Glass Committee" have had to 

 undertake. But it would be impossible for a glass-maker, 

 unacquainted with chemistry, to follow these instructions ; the 

 oxide of lead is to be purified, the purity of the boracic acid 

 is to be ascertained; in all probability the silica also will re- 

 quire purification ; all which are strictly chemical processes. 

 And even if the maker of optical glass could rely upon the 

 chemical manufacturer for these articles, the process itself re- 

 quires the possession of some degree of chemical knowledge 

 for its successful performance ; and especially to enable the 

 conductor of it to apply the principles and general rules of 

 practice laid down by Mr. Faraday, to the particular exigen- 

 cies of his own operations. The minute holes which often 

 exist in the platinum vessels employed, are to be closed by 

 little patches of that metal soldered with gold ; an oxygenating 

 atmosphere must be maintained about the glass, while remain- 

 ing fused in the finishing furnace ; the current of fresh air 

 supplying this atmosphere must first be cleansed from dust 

 and soot, by passing close to the surface of acid or saline solu- 

 tions, or else striae will be formed in the glass ; and many more 



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