88 THE AMEKICAN MONTHLY [April, 



a reflecting mirror at an angle of 45° witli the optical axis of the mi- 

 croscope. Some are made to carry a small min'or the size of the pupil 

 of the eye, others of larger extent, but with all it is necessary to keep 

 the eye in a fixed position till the drawing is finished. The plan of 

 proceeding is as follows : The microscope being inclined until it comes 

 to a horizontal position, the cap of the eye-piece removed, and the 

 camera lucida put on, it must then be determined to what extent the 

 drawing is to be enlarged. If it is to be the size it is magnified, the 

 same distance must be maintained between the camera lucida and the 

 paper as exists between the camera lucida and the object magnified ; 

 but by increasing the distance between the camera lucida and the paper 

 the magnification of the drawing can be increased proportionately. 

 Thus, if the eye piece carrying the camera lucida be projected beyond 

 the edge of the table, the drawing can be made large enough for a dia- 

 gram, but the pencil must be elongated to reach the paper oh the floor, 

 and the hand and eye must be very steady in order to successfully ac- 

 complish such an enlarged drawing. A better plan is to invert a small 

 simple microscope carrying the object to be drawn, and, on illuminat- 

 ing this in a dark room, cast its image on drawing-paper, then in pro- 

 portion as the microscope is elevated above the table so will the en- 

 largement be increased ; not only this, but the natural colors of the ob- 

 ject may be painted in. An exceedingly simple and efiicient camera 

 lucida may be constructed by a cap fitting the eye-piece, carrying a 

 square ofxover-glass at an angle of 45°. This, if broken, can be easily 

 replaced. Its upper surface reflects the image of the object, which, on 

 looking through the thin glass, appears on the drawing-paper beneath, 

 and if this paper is fixed to a drawing-board with the usual pins, the 

 drawing may be discontinued and resumed at leisure, a few trials being 

 suflicient to bring about a readjustment of the image to the outlines. 



Information on other forms is given in Dr. Carpenter's work. In 

 drawing with the camera lucida it is important to so arrange two lamps 

 that, while one dimly but clearly illuminates the object, the other should 

 throw the fullest light on the pencil ; but the apportionment had better 

 be left to individual requirements. It however aids to have the cedar- 

 wood drawing-pencil freshly cut, that the light wood, shining up 

 through the under surface of the reflector, may be a guide to its where- 

 abouts. Many beautiful drawings, full of detail, have been made by 

 simply copying the image, as seen in the field of the miscroscope, by 

 dropping into the eye-piece in the focus of the eye-glass a circle of glass 

 ruled in equal squares, and copying the image as a map is copied. 

 Whatever method is employed the drawing entails a vast amount of 

 careful labor and a great expenditure of time. Errors may creep in, 

 and therefore photo-micrography, or. the art of photographing micro- 

 scopical enlargements, comes in to insure complete veracity with a sav- 

 ing of labor. 



Photo-micrography. — This is the converse of micro-photography 

 (the making of such small photographs as to require the aid of the 

 microscope to render them visible) , while photo-micrography is ap- 

 plied to the portrayal of microscopic specimens by photographic enlarge- 

 ment. The reason for mentioning this distinction is to correct an 

 impression very generally prevalent that these terms are mutually con-^ 

 vertible and may be used with indifference. 



