252 The Microscope. 



now allowed to cool, when the cover will be ready for use. It will,- 

 of course, be understood that a quantity of rings and covers are thus^ 

 prepared and held in reserve; in fact it is to be hoped that the 

 manufacturers of microscopists' supplies will furnish the rings and 

 covers thus prepared ready for instant use. 



The object to be protected is attached to the slide by means of 

 cement in the usual way. A ring containing a glass cover is arranged 

 over the object and the heating tool is warmed and placed upon the 

 outer flange of the ring as shown in the sectional view, Fig. 2. By 

 this means sufficient heat is imparted to the ring to melt the shellac 

 upon that portion touched by the heating tool, and cause it to attach 

 itself to the glass slide. It is the work of an instant to cover an 

 object in this way, and the slide needs no further finish; but the- 

 operator may, if he chooses, lacquer the rings to prevent them from 

 tarnishing. A thin ring provided with the coating of shellac may 

 be applied to an ordinary balsam mount to increase its security. 



By applying a suitable cement to the ring, a liquid-cell may be- 

 made. The object to be mounted in the liquid-cell is wet with the 

 liquid and placed on the slide, the ring is then secured in the man- 

 ner above described, and the liquid is afterward introduced into the 

 cell through an aperture previously made in the side of the ring; 

 this aperture is stopped with cement, applied with a hot wire or 

 needle. 



It is often desirable to diminish the magnifying power of an 

 objective, and at the same time increase its penetration. For example, 

 if one possesses a one and a half or two-inch objective and desires 

 to examine objects like minerals in the natural state, ciystals, seeds, 

 etc., he will find it necessary to focus up and down upon the object 

 to see it in all its parts, a three or four-inch objective would fui'nish 

 the desired power but it is not at hand. To increase the focal length 

 and at the same time enlarge the field and deepen the focus it is 

 only necessary to place a double-convex lens of say five-inch focus 

 about half way down the draw-tube; the action of such a lens is the 

 reverse of that of an amplifier. 



ABSTRACTS, 



COLOSSAL NERVE-FIBRES OF THE EARTH-WORM. 



Prof. F. Leydig, after referring to the views of other 

 anatomists, gives an account of his own re-examination of 

 the colossal nerve- fibres of the ventral ganglionic chain of 



