December 19, 1884.] 



SCIENCE 



541 



laboratory, to hold glass retorts, tubes, etc. The iron 

 rod rests upon the floor, occupies very little space, and 

 can be moved to any convenient focusing distance. 

 A similar stand supports the horizontal elbow of the 

 stove-pipe. The tube of the microscope should be 

 blackened * inside as in micro-photography. The 

 microscope is handled in every way as usual in 

 respect to stage movement, fine adjustment, etc. 



The great difficulty with the apparatus consists in 

 trying to prevent the reflection of superfluous light. 

 To obviate this, a pasteboard box, B, six by six by eight 

 inches, is readily cut to fit closely over the plano- 

 convex lens and the back of the microscope stage, 

 thus enclosing the microscope reflector, and allowing 

 it room to be focused properly when the lid of the 

 box is removed. It is also advisable to fit a sheet of 

 pasteboard, P, tightly over the microscope tube at 

 right angles to it, in order to cut off the rays which 

 escape around the object illuminated, pass along the 

 axis of vision outside of the tube, and tend to blur 

 the image on the screen. 



be moistened with water, or covered with a thin coat 

 of transparent varnish laid over the ground surface. 

 The image may also be received upon white glazed 

 paper, but this is less clear. 



For demonstration on a larger scale, an oxy-hydro- 

 gen light can of course be used, or some form of 

 electric light. The arc-light is not sufficiently steady, 

 and the incandescent light requires a great deal of 

 storage-room for batteries. The light above described 

 shines with thirty-six candle power, is clear and 

 steady, and serves every ordinary purpose: the circu- 

 lation in the frog's foot, varieties of epithelium, 

 injected lung tissue, tubercle, plant-cells, etc., may 

 all be clearly shown. The colors of stained or in- 

 jected specimens come out distinctly. 



The principle of this apparatus is by no means 

 new; but its application is made so easily within the 

 reach of any one who owns a microscope, that it is 

 especially recommended to instructors in schools and 

 colleges. W. G. Thompson, M.D. 



25 West 26th Street, New York. 



Ji, outline of paper "box to enclose mirror; C, collar to support 

 stovepipe; E, elbow through which chimney may he re- 

 moved; F, funnel for filling lamp; 67, ground-glass screen; 

 J/, reflector inside of stove-pipe (posterior surface) ; P, paste- 

 board screen; X, hole in stove-pipe where lens is inserted. 



Dr. J. West Koosevelt (to whom the larger part 

 of the ingenuity of this apparatus is due) and the 

 writer have for some time made constant use of it 

 for instructing students. Physiological, histological, 

 pathological, and botanical specimens may be ciearly 

 shown. A number of students can look on at once. 

 The slides are rapidly changed, and students and 

 instructor may always be sure that they are discuss- 

 ing the same particular cell; which, unfortunately, is 

 not the case when a beginner in the use of the micro- 

 scope looks through the instrument alone. The 

 apparatus may readily be constructed by any one for 

 about five dollars: it is easily portable, and always 

 ready for use in any darkened room. It is possible 

 to throw the light from the lens X directly upon 

 the object without the intervention of the micro- 

 scope reflector, but the reflector facilitates focusing. 

 Objectives of wide aperture are preferable. With 

 some lenses, the use of the eye-piece adds distinctness, 

 but in most cases it cuts out too much light. An 

 Abbe illuminator may be inserted. The image on 

 the screen G is seen most distinctly upon the farther 

 side; and some objects become clearer if the screen 



QUINTINO SELLA. 



Quintino Sella was born JuLy 27, 1827, at 

 Mosso Superiore, a little village on the Biel- 

 lese mountains, and pursued his early studies at 

 Biella, evincing a special aptitude for the clas- 

 sics. Later he completed a course of stud}' in 

 mathematics and physics at the Turin univer- 

 sity, and obtained the degree of hydraulic 

 engineer. He then entered the school of mines 

 at Paris, and passed the following five years, 

 partly in study, partly in travelling through 

 Germany and England. His studies were 

 much interrupted by the political excitement of 

 1848, and he was an interested witness of all 

 the stirring events from the fall of Louis Phi- 

 lippe to the proclamation of the second empire. 

 At Paris he made the acquaintance of Gastaldi, 

 with w T hose co-operation he later founded the 

 Valentino museum. After his return to his 

 home in 1852, he would have entered the service 

 of the royal corps of mining engineers ; but 

 Savoy being the only district vacant, and not 

 being able, on account of private business and 

 his somewhat impaired health, to reside there 

 during the winter, he remained at Turin, where 

 he became professor of geometiT at the tech- 

 nical institute, and where he married Clotilde 

 Rey. In June of the next }-ear he went to 

 Savoy, and remained till the autumn, when he 

 was appointed temporarily professor of math- 

 ematics at the university of Turin. In 1856 

 he was admitted into the corps of mining engi- 



