PROCURING OBJECTS. 85 



In order to show the stomachs, cilia, &c., of animalcule 

 under the microscope, rub some pure sap-green or carmine on 

 a palette or plate of glass, and add a few drops of water. If 

 the glass 'be now held on one side, a portion of the coloring 

 matter may be put into the water on the slide containing the 

 animalculse. If they be vorticellse or rotiferse, the particles of 

 coloring matter will show the vibratile actions of the cilia, 

 whilst other particles swallowed by the animals, will give a 

 rich tint to the compartments of their alimentary canal. 



Fossil Infusoria. A great number of infusorial earths may 

 be mounted in balsam (test objects dry, however) without 

 washing, &c., but others must be repeatedly washed or digested 

 in acid. For the skeletons or shields in carbonate of lime, 

 consisting mostly of Polythalamia, or many-chambered shells, 

 Professor Ehrenberg has directed to place a drop of water on the 

 slide, and put into it as much scraped chalk as will cover the 

 fine point of a knife, spreading it out, and leaving it to rest a 

 few seconds; then withdraw the finest particles, which are 

 suspended in the water, together with most of the water, and let 

 the remainder become perfectly dry. Cover this with Canada 

 balsam, and hold it over a lamp until it becomes slightly fluid 

 without froth. 



Siliceous Shields of Infusoria, such as those in guano, 

 Richmond earth, &c., require to be well washed and boiled or 

 digested in nitric or hydrochloric acid. After this, a small 

 quantity of the sediment in which they are contained should 

 be placed on a number of slides, and those containing the best 

 specimens laid aside for mounting. In guano and Richmond 

 earth are found most beautiful saucer-shaped shells, having 

 hexagonal markings, which have received the name of Cosci- 

 nodiscus, or sieve-like disc. They vary in size from T <jth to 

 y^Qjjth of an inch in diameter. 



The polishing slate of Bilin, which is found in strata fourteen 



8 



