New method for constructing circular lenses up to 10-feet diameter for £50. Focusing power sufficient to melt metals. Wants to send 3-inch sample to JH.
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The Sir John Herschel Collection
The preparation of the print Calendar of the Correspondence of Sir John Herschel (Michael J. Crowe ed., David R. Dyck and James J. Kevin assoc. eds, Cambridge, England: Cambridge Univ. Press, 1998, viii + 828 pp) which was funded by the National Science Foundation, took ten years. It was accomplished by a team of seventeen professors, visiting scholars, graduate students, advanced undergraduates, and staff working at the University of Notre Dame.
The first online version of Calendar was created in 2009 by Dr Marvin Bolt and Steven Lucy, working at the Webster Institute of the Adler Planetarium, and it is that data that has now been reformatted for incorporation into Ɛpsilon.
Further information about Herschel, his correspondence, and the editorial method is available online here: http://historydb.adlerplanetarium.org/herschel/?p=intro
No texts of Herschel’s letters are currently available through Ɛpsilon.
New method for constructing circular lenses up to 10-feet diameter for £50. Focusing power sufficient to melt metals. Wants to send 3-inch sample to JH.
Sends small lens. Its components neither parallel nor concentric; contains water. Suggests new polishing method. Estimates 4-foot lens would cost £7-£8. [JH Note: Tested and returned lens. Noted advantages and deficiencies and suggests improvements. Listed others who built similar lenses.]
Lens safely returned. Not aware of lenses in 1851 Exhibition or of C. F. Sturm's solid lenses. Notes advantages of plate glass. Offers to make three foot by three foot square lens. Recognizes limitations for use in astronomy; hopes for other applications.