The Microscope. 251 



be shut. By artificial light in a dark room both eyes can be 

 kept open. He then makes a statement that certainly does not 

 accord with our experience. How does it with yours ? He says, 

 " One hour of steady hard work with the microscope by diffused 

 daylight will tire you more than a whole day's work in a dark 

 room by lamplight." 



A Pocket Field Microscope. — Mr. T. Hippesley describes 

 a pocket microscope that will magnify a hundred diameters and 

 is very useful in the search for infusoria, etc. The instrument 

 is made by bending a piece of thin metal five inches long by one- 

 half inch wide into the form of the letter V ; make two circular 

 holes, one-tenth inches, one in each arm, opposite each other, 

 so that when the arms are closed together by pressure the holes 

 shall meet exactly. Now place a drop of water in one hole, tak- 

 ing care not to wet more than its interior circumference. The 

 water will assume the form of a perfect double convex lens, of 

 focal length, varying from ^ to 1-10 inch. The end of one arm 

 is bent inward so as to form a " stop," which when the arms are 

 pressed towards each other to effect the focal adjustment, pre-, 

 vents a contact which would destroy the lenticular form. 



Preparing the Tail of a Puppy. — Harden the tail in alco- 

 hol for one week ; soak in water ; then place in a 1-6 per cent, 

 solution of chromic acid, to every ounce of which add five drops 

 of nitric acid ; change this mixture frequently ; when bone is soft 

 soak in water and re-harden in alcohol ; cut the sections and 

 stain with carmine; fix the staining by adding mixture of five 

 parts alcohol and one part hydrochloric acid; when scarlet, then 

 wash in alcohol to remove acid and stain again in sulph-indigo- 

 tate of soda, two drops to ounce of alcohol; let it remain here 

 for four or six hours ; then place in absolute alcohol, cleared in 

 oil of cloves and mount in balsam. 



To Prepare Sections of the Eye. — The whole eye is placed 

 in Miieler's fluid for 3 or 4 weeks, then cut with a sharp knife 

 into two symmetrical parts, which are washed to remove yel- 

 low color. This may be hastened by placing them in a 1 per 

 cent, solution of chloral for several minutes. They are now 

 placed in ordinary alcohol for one day, and then transferred to 

 absolute alcohol for another day. Sections are cut, after the tis- 



