OF MICROSCOPIC OBJECTS. 47 



Half a dozen to a dozen filters, each with its specimen, can be in 

 process at the same time ; and the distillation of the recovered 

 benzole progresses as quickly as the filtration, which was practi- 

 cally proved on the occasion named. Great caution in the use of 

 benzole is to be taken in the approach of lights to the inflamma- 

 ble vapour. 



After the Foraminifera and calcareous forms have been removed, 

 the residue may be treated with acids and levigation in the usual 

 manner, to obtain siliceous forms and discs, if there are any 

 present ; but to facilitate their deposition, and to avoid the loss 

 of any minute atoms suspended in the washings, I would suggest 

 the use of filtration. The conical filter is unsuitable, as the parti- 

 cles would spread over too great a surface of paper ; but glass 

 tubes open at both ends (such as broken test-tubes) will be found 

 to answer, the broad end covered with filtering paper, and over 

 that a slip of muslin tied on with a thread to facilitate the passage 

 of the water and prevent the risk of breaking the paper. Suspend 

 the tube over a suitable vessel through a hole cut in thin wood or 

 cardboard, pour in the washings, which can be thus filtered and 

 then dried. The cloth must be carefully removed, the paper cut 

 round the edges of the tube, and the diatoms on the paper disc 

 may be removed by a camel-hair pencil or otherwise, ready for 

 mounting. Thus many objects may be preserved which would 

 be either washed away or only be obtained by a more tedious 

 process. 



Such is Mr. Dale's method of cleaning the soundings from the 

 tallow, and as it thoroughly accomplishes its end, and is alike 

 effective and not injurious to Foraminifera and diatoms, it may be 

 safely recommended. The weak solution of caustic potash before 

 advised for Foraminifera, must not be used where it is desired to 

 preserve the diatoms, as they would certainly be injured, or de- 

 stroyed altogether, if this agent were employed. 



In fixing the Foraminifera upon the slide, no better plan can be 

 followed than the " dry cells" and gum recommended in the early 

 parts of this chapter. Owing to their thickness and composition, 

 most of them are opaque objects only ; but they are exquisitely 

 beautiful, and require no particular care, except in allowing the 

 cell, &c., to be perfectly dry, when the cover is placed upon it, or 



