Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration / by Lewis Wright.

  • Wright, Lewis, 1838-1905.
Date:
1901
Catalogue details

Licence: Public Domain Mark

Credit: Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration / by Lewis Wright. Source: Wellcome Collection.

    430/488 (page 418)
    ‘ mantles,’ reaching 70-candle power, this form of light, which is so convenient for constant work in one place (as a class-room), owing to nothing beyond a gas-tap being needed, has become of more value. The light is sufficient for a very fair 8-ft. disc. The great fragility of the mantles remains the chief drawback, and requires the most extreme care in moving the apparatus. The definition is not, as a rule, quite so good as with other lights, especially with double-piano Fig. 233 condensers; the Herschel form with meniscus back does the best work with it. With all these drawbacks, for fixed work in a small room no light is so convenient as this, and the mantles now cost only Is. 3d. each. Acetylene Gas.—Recent experiments by Professor Y. Lewes hold out expectations of a new and convenient light for the lantern ; one cubic foot per hour of this gas producing a small flame of about 70-candle power, while possibly more gas in several flames may