250 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE. 



and lay on the other glass ; any curious objects may be 

 preserved in this way without danger of their perishing ; talc 

 may be applied, as in the preceding article, for deep powers. 



Opaque Objects may be prepared for examination in the 

 following way ; cut a card or piece of stiff paper the size of 

 the object to be examined ; put a little gum water upon it, 

 and the insect will adhere to it, and may be viewed by plac- 

 ing it under the microscope, on the stage ; or, by means of 

 the steel forceps, it may be held in the hand. For viewing 

 minute opaque objects with a high power, with the body, a 

 strong light must be condensed and thrown down upon 

 them by means of a lens, but the single power or lens is 

 better adapted for that purpose. A condenser can be 

 applied to the microscope, by which means a greater power 

 can be used with the body for viewing opaque objects. To 

 preserve curious opaque objects, they may be fixed on some 

 slips of glass with gum water, and another glass placed 

 over them, cemented together with sealing-wax. 



Active Molecules in Organic and Inorganic Bodies, disco- 

 vered by Robert Brown, Esq., F.R.S., &c. &c. This inde- 

 fatigable gentleman, in prosecuting his elaborate researches 

 into the vegetable kingdom, was led to infer (from circum- 

 stances connected with the investigation of the pollen plants 

 suspended in water), that the same active molecules might 

 likewise exist in inorganic bodies ; he has not been disap- 

 pointed, having succeeded in separating them from almost 

 every known substance, such as minerals, glass, common 

 dust, soot, &c. &c. ; indeed the principal exceptions are oil, 

 resin, wax, sulphur, such of the metals as could not be 

 reduced to that minute state of division necessary for their 

 separation, and finally, bodies soluble in water. 



The process of obtaining a satisfactory view of these 

 minute active molecules is exceedingly simple, and is as 

 follows : with the head of a pin place a small drop of dis- 

 tilled or filtered water upon a slip of glass, then apply the 

 head of the pin (again dipped in the water), to the substance 

 from which the molecules are to be separated, which is 

 effected by a slight friction ; afterwards immerse the head 

 of the pin in the water upon the slip of glass, gently agitat- 

 ing it ; this will occasion the molecules to be transferred to 

 the water upon the glass, which is then in a state to be 



