lis LECTURE xr. 



is to trace cross lines on them, with the assistance of such a frame as lias been 

 described for drawing in perspective, representing the appearance of uniform 

 squares or rectangles, and to delineate in each of these the corresponding 

 parts of the object, or of the drawing which serves as a copy. 



The arts of writing and drawing, in all their varieties, are extended in 

 their performance, and perpetuated in their duration, by means of engraving 

 and printing. If there is any one circumstance to which we can peculiarly at- 

 tribute the more rapid progress of general civilisation in modern than in ancient 

 times, it is the facility of qiultiplying copies of literary productions of all 

 kinds, by the assistance of these arts. The distinguishing character of print- 

 ing consists in the employment of moveable types: the art of engraving is 

 more simple, and in some of its forms, more ancient. The Romans were in 

 the habit of using seals and stamps, for marking letters and words on wax and 

 on pottery; it was usual in the middle ages to employ perforated plates of 

 metal as patterns for guiding a brush, by means of which the capital letters 

 Avere inserted in some manuscripts, and the Chinese are said" to have been long 

 in possession of the art of printing books from wooden blocks. It was in this 

 form that printing was first introduced into Europe, in the beginning of the 

 fifteenth century. There seems to have been formerly a method of engraving 

 on wood with greater ease and accuracy than is now practised; the hatches 

 may be observed in old wooden cuts to cross each other more frequently, and 

 with greater freedom, than in modern \vorks, although some have conjectured, 

 with considerable appearance of probability, that these old engravings were 

 in reality etched in relief on metal. The art of engraving on wood is, how- 

 ever, at present in a high degree of perfection in this country, and blocks are 

 still frequently used for mathematical diagrams andother simple figures; for 

 , although they are somewhat more expensive than copper plates, they wear 

 much longer, and they have the advantage of being printed off at the same 

 time with the letter press, and of being included in the same page with the 

 text to which they belong, since the ink is applied to the projecting parts 

 only, both of these cuts and of the common printing types. 



The method of engraving on plates of pewter or of copper, and of taking 

 impressions, by means of the portion of ink retained in the furrows cut by 

 the graver, was also introduced in the fifteenth century. For dry engraving, 



