130 THE MICROSCOPE. 



but a slight disadvantage. Before mounting, make a very shal- 

 low cell of hot-paraffin and balsam, and after the cover-glass is 

 in position, ring the edge with a very little of the same material, 

 following this with repeated layers of cement, King's being pre- 

 ferred. 



There is an interesting account of this animal in the Micro- 

 scopical Journal for December, 1892, but the cut is recent. Dr. 

 Talmage has forwarded the photo-micrograph from which this 

 cut has been made by the photo-engraving process. 



DE LA FACON D'OBSERVER AU MICROSC OPE, 

 or, How to Observe With the Microscope. 



By M. F. LEMARDELEY, 

 [Translated from the French by Rene Samson.] 

 Does the microscope tire the eyes? Such is the first question 

 which presents itself to persons desirous of observing the won- 

 ders of the unseen world. Let them be reassured. The use of 

 the microscope, if our directions are followed, can but augment 

 the sensibility of the eye by practicing it to perceive without dif- 

 ficulty the dullest tin ts and the most delicate details of struct- 

 ure. The conditions for working without the least fatigue are : 

 1. — Never observe immediately after eating. 

 2. — Open both eyes during study, for the fatigue that very 

 many beginners experience is due to the effort made to keep one 

 eye closed. 

 3. — Never use too bright a light. 



4. — Work upon an unpolished and dark-colored table of such 

 a height that the ocular will be on a level with the eye by bend- 

 ing very slightly. 



How to Observe. — As has just been said, the place where one 

 works ought to present an unpolished and dark surface. Any 

 table which is a little heavy and covered with cloth or with 

 very deep gray linen will perfectly answer the purjjose. Black 

 is not so good, for the minimum of fatigue comes at the moment 

 when both eyes receive a nearly equal quantity of light. All 

 the bright objects that one has at hand (oculars, objectives, etc.,) 

 should be arranged so as not to attract the attention of the un- 

 occupied eye. 



If one observes during the day-light, he should place himself 

 at 1 metre or 1.50 m. (3 to 5 feet) from the window and he should 



