38 MICROSCOPY FOR BEGINNERS. 



piece, the hand alone guiding the wet brush, and the 

 eye taking note of the rush of the incoming wave and 

 the result. The student will soon become such an adept 

 that he will be able to add so small a supply at each 

 touch of the wet brush that the movement of the cap- 

 illary wave will not be strong enough to float the ob- 

 ject out of the field. 



But it often happens that a certain specimen is to be 

 studied for a long time, a whole evening, for instance, 

 and to be continually supplying the loss by evaporation 

 is not convenient the student often becoming so ab- 

 sorbed that he forgets this one of nature's laws until he 

 suffers the penalty, and probably loses his object. At 

 such a time an arrangement is wanted for supplying 

 fresh water continuously and without demanding much 

 attention, and such a contrivance is easily made. With 

 a triangular file cut one of the smallest homoeopathic 

 phials in two, throw away the upper half, and cement 

 the lower to a little oblong or square piece of ordinary 

 glass or broken slip. Attach this to the slide by a drop 

 of glycerine, taking care not to use too much, or the 

 square will glide out of place when inclined. Fill the 

 bottle with water, coil into it one end of a doubled, 

 loosely twisted thread of sewing-cotton, and place the 

 other end in contact with one side of the cover, as shown 

 in Fig. 3. The water will pass down the thread to one 

 edge of the cell, where it will flow under as it evapo- 

 rates from the other three sides. This usually works 

 well, the secret of success being to have the reservoir 



