f>S2 DESCRIPTION OF A PERSPECTIVE INSTRUMENT, 



pofe and for fixing the true inftrument. After this preface, I 

 ihall proceed to copy without farther remark, page 460. 

 Advantages of « An early ufe of a rule and pencil, and eafy accefs to prints 

 delineation, and or ^ rniichines, of architecture, and of implements of trades, are 

 the infpeftion of of obvious ufe in this part of education (mechanics). The 

 mTh\n g e S s. &C '° fmacnines puWifhed by the Society of Arts in London, the 

 prints in Defaguliers, Emerfon, le Spectacle de la Nature, 

 Machines approuvees par l'Acaderaie, Chambers's Dictionary,. 

 Eerthoud fur PHorlogerie, Di&ionaire des Arts et des Me- 

 tiers, may, in flicceflion, be put into the hands of children. 

 The moil Ample mould be firft felecled, and the pupils mould 

 be accuftomed to attend minutely to one print before another 

 is given to them. A proper perfon fliould carefully point out 

 and explain to them the firft prints that they examine ; they 

 may afterwards be left to themfelves. 

 Method of con- « To underftand prints of machines, a previous knowledge of 

 quHkf previous wna t IS meant by an elevation, a profile, a feclion, a perfpec- 

 information, tive view, and a (rue d'oifeau) bird's eye view, is necelfary. 

 To obtain diftinct ideas of fections, a few models of common 

 furniture, as chefts of drawers, bellows, grates, &c. may be 

 provided, and cut afunder in different directions. Children 

 eafily comprehend this part of drawing, and its ufes, which 

 may be pointed out in books of architecture ; its application 

 to the common bufinefs of life is fo various and immediate, as 

 to fix it for ever in the memory ; befides, the habit of abftrac- 

 tion, which is acquired by drawing the fections of compli- 

 cated architecture or machinery, is highly advantageous to the 

 mind. The parts which we wifh to exprefs are concealed, 

 and are fuggefted partly by the elevation or profile of the 

 figure, and partly by the connection between the end propofed 

 in the conftruction of the building, machine, &c. and the 

 means which are adapted to effecl it. 

 The art of per- *< A knowledge of perfpe&ive is to be acquired by an opera- 



a P cfn\7m r plarion 8 tion of the mind > dire % oppofite to what is necefTary in de- 

 of the merepk- lineating the fections of bodies ; the mind muft here be intent 

 "vet external only upon the objects that are delineated upon the retina, ex- 

 actly what we fee ; it muft forget or fufpend the knowledge it 

 has acquired from experience, and muft fee with the eye of 

 childhood no farther than the furface. Every perfon who is 

 accuftomed to draw in perfpective, fees external nature, when 

 jie pleafes, merely as a picture : this habit contributes much 

 2 to 



