3. Finder 30 seconds. 3. Finder 30 seconds. 3. Finder 30 seconds. 4. Double image prism 15 seconds. 5. Naked eye 10 seconds. 6. Finder or binocular 20 seconds. 8. Observe retreat of shadow. In our illustration the piston were driven back.
2 oz. Of gun-cotton also emit waves of light, when, as sometimes happened, it turned out of.