and Description of the Eidograph. 427 



of my parallelogram ; for both publicly in school did I deliver to 

 my pupils precepts in the art of delineating objects on a plane, 

 along with sound demonstrations, and at home also, privately, I 

 revealed to many the abstruser doctrines of the science. By 

 this means it happened that a general knowledge of the art got 

 abroad. I made, however, a more free communication to those 

 who were going into the Spains, and thence about to traverse 

 the eastern and western worlds for the dissemination of the Ca- 

 tholic faith, that they might have by this means a more ready 

 access to conciliate the benevolence of mankind, and thence in- 

 stil more easily truths of deeper moment into minds thus pre- 

 pared to receive them."* 



The Pantograph has no defect in its geometrical principles, 

 but, considered as an instrument for practice, it is by no means 

 perfect. It is composed of metallic bars, which turn on five 

 centres ; it is supported on six rollers turning also on centres, 

 and continually changing their direction while they move along 

 the paper ; and when the instrument is used, the force which 

 changes its figure is in some positions applied obliquely, and 

 thus acts at a disadvantage. On all these accounts, its excellence 

 as a working machine is by no means equal to the perfection of 

 its geometrical theory. Land-surveyors sometimes use it from 

 necessity, in reducing or enlarging plans, but the engraver hard- 

 ly ever employs it ; indeed, in his more delicate work, he can de- 

 rive from it very little assistance. 



In the summer of the year 1821, my attention was directed 

 to copying instruments. I found that the Pantograph was then 

 the only one used', and I formed the resolution of attempting to 

 invent a new instrument, which should be free from its imper- 

 fections. 



* The remainder of ScheineiTs first chapter contains nothing now particularly 

 interesting; it is therefore needless to continue the extract farther. 

 VOL. XIII. PART II. 3 I 



