46 The Microscope. 



of our leading preparers, who uses and recommends it. Yet 

 every slide that I have had from him finished with white zinc 

 cement has been ruined and, in most cases, the object has been 

 lost. In one or two instances I have been able to save the 

 object, but in every case the cell has betrayed the maker's con- 

 fidence. 



For some time, it may be for several 5^ears, the cell is trust- 

 worthy, then it suddenly begins to deteriorate in one of two 

 ways. The cement, after being for a long period apparently dr}?^ 

 and permanent, will begin to creep under the cover, and will 

 continue to advance with a slow but irresistable movement, until 

 the preparation is ruined. A slide in my cabinet at this writ- 

 ing was mounted in gl3'cerine three years ago, and, until within 

 three months, was apparently as sound as could be desired, yet 

 within those three months one-third of the cell has become 

 obscured by the slow encroachment of the deceitful white zinc 

 cement. 



Another equally treacherous method of showing its unscrup- 

 ulous character is by deliberately leaving the glass, carrying 

 cover and object with it, and doing it in so slow and guarded a 

 way that the microscopist learns of it only when too late. This 

 is its custom when it does not conclude to run under the cover 

 after it has been trusted for years. Without a single exception, 

 every white zinc cell that I have ever had, up to the time of this 

 writing, has been ruined in one or the other of these waj^s. I 

 now possess four. One is being spoiled by the slow entrance 

 of the cement into the cell; and three cells are gradually loosen- 

 ing themselves from the slip, a method that seems to be a favor- 

 ite one. The result will be that before lono; the slide will receive 

 a slight jar, when the cell, the cover and the object will together 

 leap into the atmosphere, and I shall probably have the satis- 

 faction of seeing them lying on the table, glycerine side down, 

 of course. 



The trouble has been extensively discussed in the journals, 

 and it is said to be due to improper methods of manufacture. 

 This maj" be, but it is then my misfortune never to have seen 

 any that was properly made. 



Dr. Frank L. James, an accomplished and expert microsco- 

 pist, states that the difficulty, by many so bitterly complained 

 of, is due to incorrect methods of manufacture. He says that 



