From:
Sir John Herschel
To:
Thomas Maclear
Date:
[17 December 1836]
Source of text:
unknown
Summary:
Setting a unit of measurement for solar radiation (the 'actine'); proposes to 'take for a unit of solar heat that which if all employed in heating a cubic inch of water exposing a horizontal surface of one square inch, to a vertical Sun during one minute would produce a dilation of one thousandth part of its volume.'
Contributor:
John Herschel Project