eonceni'wg the Art of Printing iy Cylinders. 23 



too fmall. For in this cafe the material will be fhifted one-twentieth of an inch in fifty 

 turns by the firll cylinder, and the fame quantity in the contrary direftion by the fecond ; 

 a quantity upon the whole quite fufficient to deftroy the eftetl of the colours in the pro- 

 grefs of one fmgle piece. Such minute diflerences can hardly be avoided in the lirft in- 

 ftance ; in addition to wliich we may place the varying dimenfions of the printing cylinder, 

 if not made of metal ; and of the great clothed cylinder, which in efFea has a larger or 

 fmaller tfiameter in proportion to the prcflurc which operates to render its eladic covering 

 either thicker or thinner. The only method of diminifliing thefe evils feems to be, that 

 all the printing, cylinders fhould by dimenfion or preflure, or both, be made to draw 

 the fame way, the outer cylinder mod, and the others gradually lefs and lefs, fo that the 

 material fliould have a tendency to apply itfelf more tightly during its paflage throiigli 

 the apparatus. 



The application of the colour to the furface of a cylinder block is attended with fome 

 dilTicuky. An ingenious mechanic may contrive various means to produce the aftion of 

 dabbing, if required. When a (lufled cylinder covered with cloth is made to revolve in 

 the colour, and thence after paffing a fcraper to apply itfelf to the block cylinder, it is 

 found to be no inconfidcrable difficulty that its dimenfions change, and its covering becomes 

 wrinkled by the adion of the fcraper as well as that of the block. A better method, 

 therefore, confifts in a revolving web of woollen cloth, like a jack-towel, flretched over 

 three horizontal cylinders parallel to each other, two of which fupport the elaftic furface 

 of the web, which in its revolution accompanies the block cylinder, and the other fervea 

 to guide the fame web to the colour, or a cylinder revolving in it. This method would 

 be very eafy and pleafant in its operation, if it were not for a property common to all 

 ftraps which revolve on the furface of two or more wheels. Thefe are obferved always 

 to feek the highefl: place ; fo that if a cutler's wheel were made with a groove to carry a 

 ftrap, inftead of a round edge, the ftrap would infallibly mount the ledge, inftead of re- 

 maining in the groove*. On this principle, the web would very fpeedily fliift itfelf to 

 one end of the cylinders, if it were not confined fideways, or the lower roller were not 

 made confiderably thickeft in the middle, and gradually tapering towards its extremities. 

 This laft fimple expedient is not without its difficulties ; but as I have not adually tried it, I 

 (hall defer entering into any difcuffion on that head. 



Tlie running of the paper or piece-goods towards one end of the leading cylinder is 

 alfo one of the greateft difficulties attending this method of printing. It is not perfedly 

 removed by taperi?ig the leading cylinders. 



Tlie nature of the trade of paper-ftaining in this country, which requires a large fum to 

 be immediately veiled in the payment of the excifc duty, and confequently prevents any confi- 

 derabie (lock from being manufaftured until orders are actually received, and the varying 

 fafhions in printed callicoes, whicli render the expence of cutting the block by far the hea- 

 vieft part of the dilburfement for printing, are probably the chief reafons why manufac- 

 turers in this country have been lefs folicitous for the conllrudtion of machines calculated 

 to afford profit only in the cafe of very numerous impreffioiis. The phyfical difficulties of 

 thia art have likewife confpired, in no fmall degree, to prevent its having been applied in 

 the large way to any but a few fimple defigns of the fort called running patterns in one colour. 



• Till! curious ctfeit arilti ficm a (Itxiiri; (.roduccd in tlif cil^it. uf tin; lUap, by the citvatcd pan ot tlic whtti 

 v.liich throws the advancing partcif the ftrap more and more towards that elevation. It cannot be explained 

 in a few word., but may cafily be fccii by wrapping a ftraiglit (lip of paper round an extinguiftier or any other 



An 



