Please convey thanks to the Society for the Diffusion of Useful Knowledge for its star maps. Finds them preferable to [Johann] Bode's maps, 'which are full of egregious errors.'

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.'

Testing whether an actinometer with a glass back is more accurate than one without.