ZOOLOGY AND BOTANY, MICROSCOPY, ETC, 



899 



processes botla in the case of recent and fossil forms. In a later 

 article of 16 pages * Herr Debes describes the various mounting 

 media, and gives directions for mounting diatoms. The articles cannot 

 be usefully abstracted. 



Gowen's Microtome. f — Mr. F, H. Gowen, considering that the 

 use of paraffin for imbedding is attended with difficulties on account 

 of its becoming loose in the microtome, has made a microtome in 

 which the difficulties are overcome. 



A hole is turned about half-way through the table of a microtome, 

 and into this a tube is screwed, forming the well. The hole through 

 the remainder of the table, forming the mouth of the well, is turned 

 with sufficient " gather," or taper, to take up the shrinkage of the 

 paraffin. On the upper side of the piston a dovetailed groove is 

 turned. The column of paraffin receives no support from the tube, 

 but is securely held by the piston at one end and by the contracted 

 mouth of the well-hole at the other. (Diameter at the top, • 9 in., 

 tapering from diameter of 0* 92 in. Length of taper, 0* 15 in.) 



Jacobs's Freezing Microtome.t — Dr. F. 0. Jacobs has devised the 

 freezing microtome shown in figs. 215 and 216. It consists of a 

 copper rod A, 2 in. or more in diameter, and 6 in. high, inclosed by 



Fig. 215. 



an inner zinc and an outer brass tank. Above is the table D, work- 

 ing on a fine screw. Through the centre of the table passes a 

 narrower portion of the copper rod p. 



When the inner tank is filled with a mixture of salt, ice, and water, 

 the temperature of the copper rod is so reduced as to freeze any 

 object F jdaced on its upper end. The size of the rod is such that 

 its temperature will remain very steady for from four to six hours, 

 without any further care on the part of the operator. 



• HedwiKia, xxiv. (1885) pp. 151-CO. 



t Amcr. Mon. Micr. Journ., vi. (1885) p. 156. 



X Amer. Natural., xix. (1885) pp. 734-(; (2 figs.). 



