Ch. XII] HISTORY OF LENSES AND MICROSCOPES 439 



and also his own combination of convex lenses. Scheiner (1626- 

 1630) used them for projecting images of the sun so that he could 

 draw the spots. See also Hooke, Trans. Roy. Soc, 1668, p. 741. 



Naturally, with the perfecting of objectives (1824 and onward), 

 and the finding of more powerful artificial lights (lime light, 1824, 

 electric fight, especially since 1880), the projection microscope is coming 

 to be used more and more. 



§ 705. Drawing magnified images. — The first drawings made by 

 the aid of the microscope were free-hand. Examples of the drawings 

 may be seen in the work of BoreUus, and in facsimiles shown in the 

 Journal of the Royal Microscopical Society, 1915, pp. 317-340. The 

 desire for accuracy and ease in tracing outlines of microscopic images 

 comparable with those so easily attained with the real images of 

 the projection microscope led to the invention of the camera lucida, 

 by which the microscopic field and the drawing field, pencil, etc., can 

 be superposed. The first one invented is still used. It is the Wollas- 

 tbn form (fig. 99), and was described by WoUaston in Nicholson's 

 Journal, 1807, pp. 1-5. The other form shown in fig. 100 was de- 

 scribed in principle by G. Burch, Jour. Quek Micr. Club, 1878, 

 p. 47; and by Dippel in the Bot. Centrlbl. 1882, pp. 242-3. 



Drawing with the projection apparatus has been practised from its 

 first invention. Indeed, in all those who described such apparatus, 

 the great help that was to be gained in drawing was emphasized. Both 

 eyes can be used, and perfect freedom of the artist is enjoyed, which 

 is in marked contrast with camera lucida drawing. For the early 

 appreciation of projection apparatus and the camera obscura for 

 drawing see: Barbaro, 1568 (§ 7osa); Kepler, 1611 (§ 7osb); Scheiner, 

 1626-1630; Robert Hooke, 1668; Baker, 1742 (§705c); Adams, 

 1746; Goring and Pritchard, 1837; ChevaUer, 1839. 



705a. Daniel Barbaro. — In his work, La pratica della perspettiva, Venice, 

 1568 Ch. V, p. 192, Barbaro says: "Take an old man's glass, convex on 

 both sides, not concave like the glasses of youths of short sight, fix the convex 

 glass in a hole, close all the windows so that no light may enter except through .the 

 lens Now take a sheet of white paper and bring it toward the lens until all outside 

 the house is clearly seen. When the prope? position is found you wiU see the images 

 on the paper as they are, and the gradations in colors, shadows, movements, clouds, 

 the rippling of waters, birds flying, and everything that can be seen. For this 

 experiment the sun must be clear and bright, for the sunlight has great power in 



