OF THE MICROSCOPE. 175 



Care of the Microscope. A microscope, when not in 

 use, should always be kept well covered, either in its case or 

 under a suitable cover. There is no more convenient mode of 

 keeping a microscope than to stand it upon a cloth mat, and 

 cover it with a glass shade. It is thus kept free from dust and 

 vapors, and is always ready for use; but when it is kept in its 

 case, and especially if it has to be screwed together, interesting, 

 valuable, or even important objects, will often fail to be ex- 

 amined, simply because too much time and labor are necessary 

 to prepare for the operation. 



A good microscope should be so carefully protected, that it 

 shall rarely require to be cleaned or dusted, as this wears off 

 the lacquer, and exposes the metal, which, when thus uncov- 

 ered, soon begins to tarnish. When dusting or cleaning becomes 

 absolutely necessary, chamois leather, or a very fine old linen 

 or silk handkerchief is most suitable. Never use coarse cloths, 

 or those that have been lying about exposed to dust and dirt. 



The lenses should be kept in their boxes when not in use, 

 and when they are attached to the microscope, great care 

 should be taken to keep them from coming into contact with 

 liquids. In order to prevent the latter accident as far as pos- 

 sible, never examine liquids unless when they are covered with 

 thin glass. In the pursuit of micro- chemical studies, the 

 microscopist has frequently to deal with liquids that corrode 

 metals, and even glass. In well-appointed laboratories inverted 

 microscopes are used in such cases, but with ordinary instru- 

 ments, special means must be employed. The object should be 

 laid on a large piece of thin plate glass, and the brass work of 

 the objective should be coated with oil. The rest of the metal 

 work may be protected with oiled silk or thin india-rubber. 



When liquids which corrode glass are used, the front of the 

 objective should be protected by means of a very thin leaf of the 

 best mica, which may be attached either by glycerine or balsam. 



These, however, are exceptional precautions. In ordinary 

 work it is sufficient to see that the lenses and metal work are 

 kept free from stains and finger marks. 



Never touch with the fingers the surface of any lenses, either 

 eye-pieces or objectives, as this will be certain to soil them. Use 

 soft camel-hair brushes to remove particles of dust, etc. Where 



