184 



THE AMERICAN MONTHLY 



SCIENCE-GOSSIP. 



[Oct. 



A Cheap Polariscope. — The following- cheap polariscope 

 will be found to g-ive first-class results: — Cut 20 to 25 

 pieces of thin g-lass, 18mm by 12 mm. Now make a card- 

 board tube from a marked card, as shown below. 



The pieces of g-lass should now be fixed in tube with 

 strips of card shown in sketch. If all is done rig-ht, the 

 g-lass will be at an ang-le of 35 deg-rees. Of course, two 

 may be required. The square tube can be fastened in a 

 round tube to fit the microscope. — Eng. Machanic. 



Carborundum Crystals. — The Physikalish-Techniche 

 Reichsanstalt is now using- carborundum crystals to a 

 g-reat extent to replace diamonds in the producing- of finely 

 divided scales. Small flat hexag-onal crystals are chosen of 

 from half to one mm. side and mounted in a steel holder by 

 means of a drop of shellac. The lines are said to be much 

 more even than those produced by a diamond ; they have 

 been examined when mag-nified fifty times and found to 

 be still sharply defined. 



Sheep Scab. — The disease commonly called sheep scab 

 is the mang-e, or scabies, of the sheep. It is a contag-ious 

 skin disease caused by a microscopic parasitic mite. This 

 disease is one of the oldest known, most prevalent and 

 most injurious maladies which affects this species of ani- 

 mals. It has been well known for many centuries, and 

 references to it are found in the earlier writing^s, including- 

 the Bible, where we find, in Leviticus xxii : 22, the use of 

 scabbed sheep forbidden in sacrifices. Some think that 

 the mite which causes the disease was known to Aristotle, 

 322 B. C. The errors and uncertainties which came down 



