1022 



SUMMAEY OF CUERENT BE8EAE0HES BELATING TO 



2-6 cm. in diameter, and magnifying from 1-2 times, whose side is provided 

 with a contrivance for holding a copying needle, a protractor, &c. 



While hitherto the architect, in using millimetre paper, must hold 

 separately in his hands a magnif^ying glass and needle, while the engraver 

 holds the engraving tool inclined in one hand and the magnifying glass in 

 the other, or must work imder a large lens standing on three feet, it is 

 now possible, by a firm connection between the lens and needle or other 



Fig. 241. 



instrument, to draw directly with one hand, and under the lens. One 

 of these lenses is shown in section at A, the glass is set obliquely, the 

 needle a being in the focus. The stud s, projecting a little near the 

 glass, is for the purpose of preventing the instrument from leaving the 

 position coinciding with the plane of the drawing. For architects and 

 engineers is provided a small compass h (about 2 cm.), for laying off 

 parallel divisions, for making smaller scales, and the like. In these cases 

 it is substituted for the needle. In like manner, for reading parallel 

 divisions, for estimating areas, or revising maps, a finely divided, prismatic, 

 ivory rule c can be placed under the glass B. In this case the plane 

 of the lens must be perpendicular to the axis of the tube. For draughts- 

 men a parallel drawing-pen, something like h, is used, which gives several 

 lines at once, perfectly parallel and close together ; or a drawing-pen with 

 which the smallest names, such as boundary stones and figures, can be 

 made neatly and exactly. Thus a whole series of instruments can be used 

 -nith the lens. For instance, a naturalist can use with it a knife or other 

 instrument. 



Henxeguy. — Sur un nouveau Microscope de voyage construit par Dumaige.. (On a 

 new travelling Microscoi^e made by Dumaige.) CR. Soc. Biol., IV. (1887) No. 7. 



Linnaeus's Microscope. 



[At the Pittsburg meeting of the American Society of Microscopists, "a very 

 c'iriou.s Microscope, once the property of Linnseus, was described by 0. C. 

 Mellor," President of the Iron City Microscopical Society.] 



Microscope, VII. (1887) p. 271. 



C2j Eye-pieces and Objectives. 



Thickness of cover-glass for whicli unadjustable objectives are cor- 

 rected.* — Prof. S. H. Gage communicated to the Pittsburg Meeting of the 

 American Society of Microscopists the following paper : — " As the thick- 



* Microscope, vii. (1887) pp. 2'J2-o. 



