228 Objects for the Microscope. 



removed with blotting paper. When the crystals are dry, 

 the Canada balsam, previously made thin with ether, may 

 be applied without heat. 



BORAX, OR BI-BORATE OF SODA, 



is soluble in twelve times its weight of cold and twice its 

 weight of boiling water, and crystallizes in very perfect 

 forms of oblique octohedral prisms. Dissolved in alcohol, 

 and dropped on a slide, it crystallizes immediately. 



BORACIC ACID 



is the acid of the salt borax, and is prepared by mixing 

 three parts of borax dissolved in twelve parts of boiling 

 water with one part of sulphuric acid. 



When a little phosphoric acid is added to the boracic 

 acid, and the solution dropped upon a slide, then laid upon 

 a warm iron plate, most beautiful discs are obtained, which 

 exhibit the cross and coloured rings under polarized light. 



From the simple solution of boracic acid we obtain 

 crystals belonging to the doubly oblique prismatic system, 

 having two optic axes. Sometimes, when rapidly crystal- 

 lized, the boracic acid forms arborescent crystals on the slide. 



SULPHATE OF MAGNESIA. 



(Epsom Salts.) 



The solution will deposit crystals belonging to the 

 rhombic system, and varying in form according to the 

 treatment in crystallizing. They polarize brilliantly with 

 the selenite stage. 



AMMONIO-PHOSPHATE OF MAGNESIA 



is a salt frequently met with in animal secretions which 

 have undergone decomposition ; they belong to the rhombic 

 system, but their varieties are endless. Stellate and pen- 

 niform crystals are frequently found in urine. 



URIC ACID, OR LITHIC ACID. 



This acid abounds in animal secretions, in the excrement 

 of birds, serpents, &c., and the urine of mollusca and 

 carnivorous mammalia. The crystals belong to the right 



