COLLECTION, EXAMINATION, ETC. 307 



light. In working by ordinary daylight it is prefer- 

 able to get the rays from a light cloud, direct sun- 

 light being too glaring to the eyes, and there is also 

 a risk of burning the object. A parabolic con- 

 denser illuminates the object very well when diffused 

 light is used; and with artificial light this condenser 

 can be used with advantage in conjunction with the 

 bull's-eye condenser. 



To facilitate the sorting of material containing 

 foraminiferal shells, it will be found advisable to use 

 a series of sieves of graduated sizes, having an 

 increasing number of meshes to the inch, as, for 

 example, 30, 60, and 120. These sieves can be 

 obtained of chemical apparatus dealers, made with 

 the sieves fitting one upon the other ; the material 

 to be sifted is placed in the top, and after a vigorous 

 shake is separated into the various grades ready for 

 examination. It must be remembered that the 

 greatest care should be taken to clean the sieves from 

 one kind of material before using them for another, 

 as all the value of our detailed examination would 

 be lost if we mixed the forms out of different 

 deposits. 



In commencing to select the specimens of 

 Foraminifera from the material prepared according 

 to the foregoing methods the sand may be thinly 

 and evenly strewn on a tray, which can be passed 

 over the stage of the microscope. This tray by 

 preference should have a rim, to prevent loss of 

 material over the sides. If the surface of the tray 

 is blackened it forms a good background. Some 



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