3?0 ^f'f Prcgrefs ef Mechanical Invention. -^Machine f«r cutllng FilfJ^ 



be well afTured of the value of what he recommends or fufFers to recommend itfcff to his 

 readers. From views of this kind, it has appeared to me, that 1 fliould do fome fervice to 

 «n a£t:ive fet of men, foiiie of whom have efFeclually farved this country, if I were con- 

 cifcly to point out the courfc of mechanical invention, in order that thofe individuals only 

 may be induced to engage in it, who poflefs the acquifitions and means to do it with fomc 

 effect. 



We will therefore fuppofe a very acute theorift, who Is not himfclf a workman, nor in 

 the habit of fuperintending the pra£lical execution of machinery, to have conceived the 

 notion of fomc' new combination of the mechanical powers to produce a determinate 

 clTedl -, and for the fake of perfpicuity, let us take the example of a machine to cut files*. 

 His firft conception will be very fimple or abftra£l;ed. He knows that the notches in a 

 file are cut with a chizel driven by the blow of a hammer, by a man whofe hands are 

 employed in applying thefe inftruments, while his foot is exerted in holding the file on an 

 anvil by means of a (trap. Hence he concludes, that it muft be a very eafy operation 60 

 fix the chizel in a machine, and caufe it to rife and fall by a lever, while a tilting hammer 

 of the proper fize and figure gives the blow. But, as his attention becomes fixed, other 

 demands arife, and the fubjeft expands before him. The file muft be fupported upon a 

 bed or mafs of iron, of wood, of lead, or other material : — it muft be fixed either by 

 fcrews or wedges, or weights, or fome other efFedual and ready contrivance : — and the 

 file itfelf, or elfe the chizel, with its apparatus for ftriking, muft be moved through equal 

 determinate fpaces during the interval between ftroke and ftroke, which may be done 

 either by a ratchet wheel or other efcapement, or by a fcrew. He muft examine all thefe 

 objefts, and his ftock of means in detail; fix upon fuch methods as he conceives to ha 

 moft deferving of preference ; combine, organize, and arrange the whole in his mind ; 

 for which purpofe folitude, daiknefs, and no fmall degree of mental effort, will be re- 

 quired : — and when this procefs is confiderably advanced, he muft have recourfe to his 

 drawing board. Meafured plans and fe£lions will then fhew many things which his 

 Imagination before difregarded. New arrangements to be made, and unforefeen difB- 

 culties to be overcome, will infallibly prefent themfelves. The firft conception, or what 

 the world calls the invention, required an infinitely fmall portion of the ability he muft 

 now exert. We will fuppofe, however, that he has completed his drawings. Still he 

 poffeffes the form of a machine only ; but whether it fliall anfwer his purpofe, depends on 

 his knowledge of his materials. Stone, wood, brafs, lead, iron forged or caft, and ftecl 

 in all its various modifications, are before him ; the general proceffes of the workfliop by 

 which firmnefs, truth, and accuracy, are alone to be obtained ; and thofe methods of 

 treatment, chemical as well as mechanical, which the feveral articles demand : — thefe and 

 numberlefs other pradlical obje£ls call for that (kill and attention, which may either 

 lead to fuccefs, or, by their deficiency, expofe him to the Ignorance or obftlnacy of his 

 workmen. If he fliould find his powers deficient under a profped fo arduous— if tc 



* Tranfaftions of the American Philof. Society, vol. ii. or Repertory, v. 184. The file is fixed on a bed 

 •f lead, and a chizel fixed at the end of a lever, is ftruck down with a hammer. This lever rifes again of itfelf 

 ky means of a fpring, and during its rife it moves a ratchet wheel, conneftid with the fupportof the bed; whi(b 

 confe^uently it ibifts together with the file after every llroke. 



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