 Thus, though the practical effect of the lamp only extends about 300 metres from its position, the field is illuminated to the extent of 700 metres, for the benefit of all placed between the light and the object. Thus a sentinel on the ramparts can see...  Journal of the Society of Arts - Page 141871Full view - About this book
 | 1871 - 598 pages
...means strict watch is kept upon the plains around the city at night, as far, in one direction, as 1000 metres beyond St. Denis. M. Bazin is now occupied...Coligny, already possesses such a signal apparatus, and thejsignals are distinctly visible at more than eight miles distance." Progress in Physics. . [January,... | |
 | 1871 - 822 pages
...on the ramparts could see about 8,000 metres from the enceinte, and, by this means, strict watch was kept upon the plains around the city at night, as...in one direction, as 1,000 metres beyond St. Denis. On one of tho French corvettes the samo apparatus was adapted for a nighttelegraph, with tho addition... | |
 | 1871 - 822 pages
...on tho ramparts could see about 8,000 metres from the enceinte, and, by this means, strict watch was kept upon the plains around the city at night, as...in one direction, as 1,000 metres beyond St. Denis. On one of the French corvettes the same apparatus was adapted for a nighttelegraph, with tho addition... | |
 | 1871 - 816 pages
...on the ramparts could see about 3,000 metres from the enceinte, and, by this means, strict watch was kept upon the plains around the city at night, as...in one direction, as 1,000 metres beyond St. Denis. On one of the French corvettes tho same apparatus was adapted for a nighttelegraph, with the addition... | |
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