The new imperial encyclopaedia, or, Dictionary of the sciences and arts : comprehending also the whole circle of miscellaneous literature ... . the workmen, it is found im-possible to give the metals either a perfectly spherical or a per-lectlv parabolical form. Heniv arises some indistincti ess of tlicimage tormed by the great speculum, which is frequently correctetlby the little one, provided they are properly niatchetl. But ifills is not done, the error will be made much woi-se; and hencemany of the Gregorian telescopes are far inferior to the Newlo-iiioii ones; namely when the specula have
The new imperial encyclopaedia, or, Dictionary of the sciences and arts : comprehending also the whole circle of miscellaneous literature ... . the workmen, it is found im-possible to give the metals either a perfectly spherical or a per-lectlv parabolical form. Heniv arises some indistincti ess of tlicimage tormed by the great speculum, which is frequently correctetlby the little one, provided they are properly niatchetl. But ifills is not done, the error will be made much woi-se; and hencemany of the Gregorian telescopes are far inferior to the Newlo-iiioii ones; namely when the specula have not been properlyadapted to each other. There is no method by which the work-man can know the specula which will fit one another wilhoutatrial ; and therefore there is a necessity for having many speculaready made of each sort, that in filling up a telescope those may bechosen which best suit each other. The brightness of any olijeetseen through a telescope, in comparison with its brightness whenseen the naked e\e, inay in all cases be easily found by thefollowing formula: Let n reprcseut the natural distance of a visi-ble Fnrir §. /^ ~T x„ / 10 .--*^\k .?;_,>>-^f- )~ - yi ?n- ,-• /s j B
Size: 1531px × 1632px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1800, bookidnewimperiale, bookyear1800
