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NOTES ON OPTICAL INSTRUMENTS. 
Iii half silvering horizon glasses cut the top edge of the foil where 
required with a razor, dragging it away towards the unsilvered surface. 
This leaves a clean sharp edge. 
Terrestrial, 'Erecting Telescope. 
Binocular Glass ; 1 Tube. 
Names of Lenses. 
1. Crossed Convex. 
2. Double Convex. 
3. Convex Meniscus. 
4. Convexo Diane. 
5. Convexo Concave. 
6. Dlano Convex. 
7. Dlano Concave. 
8. Double Concave. 
