WITH THE MICROSCOPE. 67 



ness. It consists of two rectangular glass plates 3 x 2 in and about ^' T 

 of an inch thick, separated by thin strips of glass of the same thickness, 

 cemented to the interior opposed faces. The upper plate has a small 

 hole drilled through it. One corner of the upper glass is removed, 

 and a small strip of glass, which is cemented to it in the proper place, 

 prevents the thin glass cover placed over the edge from sliding off. 

 To use the slide, fill the space between the two plates with clean 

 water introduced by means of a pipette, and also place a drop in the 

 hole to remove the air. The object being put on the top of the slide, 

 and wetted, is now to be covered with a large square of thin glass, at 

 the same time covering the hole. The slide can now be placed 

 upright, or in any position, as no water can escape. It is, in fact, 

 only a new application of the old principle of the bird-fountain. As 

 the water evaporates from under the cover, more is supplied through 

 the hole, and from time to time an air bubble enters. Thus a con- 

 stant circulation is maintained. 



Mr. Richard Beck has made one or two alterations in the growing 

 cell of Professor Smith (Quarterly Journal of Microscopical Science, 

 April, 1856). The annoyance caused by the water line obscuring the 

 view, as sometimes happens in Professor Smith's growing cell, has 

 been entirely obviated, and one or two other improvements have been 

 effected. 



Dr. John Barker, of Dublin, has contrived a very convenient, 

 efficient, and cheap growing stage, which has the advantage of allow- 

 ing the use of the ordinary glass slides. A full description of this 

 will be found in the Quarterly Journal of Microscopical Science, 

 January, 1867. Any one can make this growing stage for himself with 

 very little trouble. A segment of a largish circle is cut in a plate of 

 stout glass to form the stage. To one end of this is attached by 

 means of marine glue, a small flat glass bottle in which two little 

 holes have been drilled. These bottles may be obtained of 

 Mr. Baker, of Holborn. When water is put into the bottle, it is 

 conveyed from one of these holes to the thin glass cover under which 

 the object is to be kept moist, by means of a narrow strip of talc 

 which acts as a conductor for it. By this arrangement, any object 

 under observation may be kept moist for the space of a week, if 

 desirable. Dr. Barker's growing slide is represented in pi. XVIII, 

 fig. in. 



For some time past I have been in the habit of employing an 

 arrangement which is simpler than either of those above referred to, 

 and, in my hands at least, it has proved very efficient. A small piece 

 of glass tube is fixed with the aid of marine glue to one end of an 

 ordinary glass slide a, fig. in*, pi. XVIII. This is the reservoir for the 



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