800 SUMMAR-y OF CURRENT RESEARCHES RELATING TO 



telescopic arrangement by which the disc is approximated to the handle 

 or removed farther from it. The disc is brought near to the handle by 

 means of a screw-nut fixed at the end of the inner part of the axle, and it 

 is moved away by means of a concealed spring. The amount of this 

 motion is not more than three millimetres. The disc and axle are fitted 

 on a strong iron stand, supplied with levelling screws. 



The frame is so arranged that the disc may be used in the vertical or 

 in the horizontal position. The vertical position is, perhaps, the most 

 convenient for museum demonstration. The apparatus, when used in 

 this position for museum demonstration, is placed in a closed case. The 

 handle, with its binding screw and focusing button, are the only parts 

 of the apparatus outside the case. 



The disc is furnished with slides. These are clipped to the face of 

 the disc by means of a segmented ring. The upper surface of each 

 specimen is turned towards the observer, so that the thickness of the 

 slide is not involved in the focusing adjustments. The disc must be so 

 placed that it will be perfectly parallel to the front of the case, and the 

 light must fall on the face of the disc. The former condition is secured 

 by means of the levelling screws and a square, and the latter by having 

 the case in front of a window. 



The Microscope is fitted to a brass plate which slides in a second 

 plate fixed to the front of the case on the same level as the axle of the 

 apparatus, and at a distance equal to the semi-diameter of the disc. A 

 lateral motion of the Microscope is best caused by a wheel and rachet 

 arrangement. The possible movement is one inch. 



The Microscope, then, being fixed for any specimen, it is evident 

 that the screw button on the axis serves to focus the specimen, and is 

 similar to a fine-adjustment. Secondly, a specimen may be examined 

 from side to side by means of the lateral motion of the Microscope. 

 Thirdly, the specimen may be swept from above down by the handle 

 moving the disc ; and lastly, a whole series may be examined one after 

 another. It is quite safe to place the instrument in a museum case. 

 Ko one can injure the slides or spoil the Microscope, as the limits of 

 motion are fixed, and the student can thus study a series of specimens 

 without supervision. 



The instrument may be used in the same position for class demon- 

 stration, or it may be turned, levelled, and thus used in the horizontal 

 position hy means of an ordinary arrangement for reflected light. 



The Microscope tube is, under ordinary circumstances, so close to the 

 vertical portion of the stand, that a special stand is necessary for use in 

 the horizontal position. 



The museum case should be provided with curtains, as some preserved 

 specimens are injured by the light and heat." 



Nelson- Curties Microscope (Large Model).— This Microscope 

 (fig. 98) is the joint pi-oduction of Mr. E. M. Nelson and Mr. _C. L. 

 Curties.* It stands on a firm tripod foot, the extremities of which are 

 plugged with cork, diminishing vibration and preventing it slipping or 

 injuring a table. Depending from the trunnions is a kind of stirrup, to 

 which the Microscope is attached. This stirrup lowers the centre of 

 gravity when the Microscope is vertical or in an inclined position, and 

 gives a better balance when the instrument is horizontal for photo- 



* See this Journal, 1888, p. 691. 



