ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 643 



convenience (and for military purposes in front of the enemy, of the 

 dangers) involved in the employment of topographical maps by night 

 or in bad weather. By the aid of the new map-loup small transparent 

 diapositive maps in the shape of about 20 sq. cm. (5x4 cm.) are used 

 in lieu of large paper sheets. The microphotoscope can be used by day 

 or by night ; in the latter case, the necessary illumination is supplied by 

 a glow-lamp actuated by a dry battery. For the arrangement to work 

 conveniently, the loup must have strong magnification, and the loup- 

 map be of a minimum size. The loup has, at present, been constructed 

 of 13£ fold magnification ; it seems scarcely possible to increase this, 

 and, indeed, does not seem necessary. The composition of a sufficiently 

 grainless emulsion for the preparation of the small map diapositives 

 appropriate to the selected magnification has already revealed great 

 difficulties, but these may now be regarded as entirely overcome. The 

 diapositive lies well protected between two glass plates. The loup is, of 

 course, accommodated to the observer's eye, and, moreover, is adjustable 

 over the plane of the diapositive. For a selected position of the loup 

 175 sq. kilos, would be readable at once on a diapositive of the map of 

 the German Empire (1 : 100,000). Sheets of the map of the German 

 Empire should be first prepared as diapositive loup-maps, afterwards 

 those of the most important foreign topographical maps. On a dia- 

 positive a square-meshed net is drawn with sides corresponding to 

 2£ kilos., so that in all directions estimation of routes and elevations 

 can be made. 



Studnicka's Pancratic Preparation Microscope.* — F. K. Studnicka 

 points out that the principle involved in the lens combination described 

 in the previous article, is essentially that of a " pancratic " Microscope. 

 The term is not a new one ; pancratic Microscopes were familiar instru- 

 ments in the first half of the nineteenth century, f and were generally 

 xised as dissection-microscopes. They seem to have been found un- 

 satisfactory and to have gradually dropped out of notice. The author, 

 however, thinks that this oblivion is not deserved. He proposes to 

 accurately insert a reversed objective, by means of a simple connecting 

 piece, in the diaphragm-carrier of the Abbe illuminating apparatus, from 

 which the condenser has been removed. Both objectives thus come, 

 in this way, into the approximately proper distance from one another ; 

 at most the tube may require to be lowered a little. The side-light is 

 screened off by the side-walls of the upper iris of the illuminating 

 apparatus ; the lower objective is fairly close to the object and by rack- 

 and-pinion may be brought still closer to it. The object must be placed 

 on a special stage under the inverted objective, and this stage should be 

 fitted with supports for the hands. Such a stage can be easily im- 

 provised out of two pieces of wood and a glass plate. It is possible to 

 use the ordinary stage " pancratically," but the ordinary objective is 

 then inserted at the lower end of the draw-out tube, and the inverted 

 objective fitted to the lower end of the tube (or revolver) with a con- 

 necting piece. Tubes with rack-and-pinion movement would be most 



* Zeitschr. wiss. Mikrosk., xxi. (1904) pp. 440-4 (1 fig.). 



t Vide, e.g. Fischer, Le Microscope pancratique, Moscou, 1841 ; Hartri?. Das 

 IMikroskop, 1859. pp. 198 and 766. The ' Telemikroskop' of Deschamps (Comptes 

 Rendns. cxxs . 1900) deals with a similar lens-combination. 



