952 



EECORD OF CURRENT RESEARCHES RELATING TO 



usually will adhere to it at once, and may be examined by rotating the 

 bristle wire by means of its milled head. 



Professor H. L, Smith, in a subsequent paper,* gives some hints 

 which he thinks will greatly facilitate the use of the " finger," and 

 which, though simple, are the fruit of long experience, will save much 

 valuable time, and " conduce to general morality." 



The " bristle" or " hair" is to be held in the spring forceps, and, 

 after adjustment, a drop of sealing wax put on the forceps to bind all 

 tight. To make the " hair," cut a slip of glass, and by a spirit lamp draw 

 it out into a slender thread ; snip off the thread by a knife, so as to pre- 

 sent a bevelled edge (Fig. 3, magnified). This thread is so fine as to be 

 quite flexible, and if dirtied can easily be cleaned. It is not affected 



Fig. 3. Fig. 4. 



by moisture, applied as described presently, 

 a very importcmt point. It will often be easy to 

 pick up a diatom by simply touching the point 

 to the slide, and then by depressing the tube 

 of the instrument, causing it to slide forward 

 on the glass plate till the object is dislodged. 

 His modification of the " finger " has the 

 Society screw, and will receive any objective, 



though he prefers a f inch. (Fig. 4.) When the screw A is 

 loosened, the ring B and the hair C can be revolved, and made 

 to point towards the centre of the field in any required direction, 

 which will be found convenient for pushing a diatom into place 

 in arranging. The objective screws in at D, and by raising or 

 depressing the rod E, the point of the hair can be brought into 

 focus. It should point downwards at a slight angle. If when it has 

 been brought into focus, we unscrew the front lens of the objective 

 slightly, this will throw the point out of focus, and now the objective 

 may, by the rack, be brought down to give a distinct view of the 

 material from which the object is to be picked, icithout any danger of 

 the hair point toucliinrj it. When the object is foimd, then by turning 

 home the unscrewed front lens, the point will come into focus, and by 

 slightly racking down the tube, the point can be made to touch the 

 object, and by racking back to lift it. If dirt is raised a light tap on 

 the tube will instantly set it free, and leave the hair clean, or it may 

 be cautiously wiped off with tissue paper. One of the greatest objec- 

 * ' Am. Journ. Micr.,' iv. (1879) p. 102. 



