%g6 Dr. Herschel’s Observations to investigate 
and a single hole was made in the middle of the moveable 
piece No. 4, of the photometer described in my last paper..* 
I now viewed the opening and shallow in the sun, and im- 
mediately after went to the photometer, to examine the artificial 
phenomenon. By withdrawing the farthest vane, I diminished 
its illumination, till I found the small visible rim about the velvet 
less luminous than the paper of the first vane, in the same 
proportion as I judged the shallow to be less bright than 
the rest of the sun. Then, going alternately many times to the 
telescope and to the photometer, and making such little altera- 
tions in the apparatus as I thought necessary, I obtained at 
last a result, which shewed that the rim of paper representing 
the shallow reflected 4 69 parts of the incident light. 
Hence, if the superior self-luminous clouds of the sun throw 
the same quantity of light on the inferior region of opaque 
solar clouds as they send to us, it follows, that those inferior 
clouds of which the shallows are composed, reflect about 4 69 
rays out of every thousand they receive. 
With regard to the solar surface which we see in the openings, 
I also found that black worsted, which, by my lately published 
tables, reflects 16 rays out of a thousand, was not dark enough, 
compared to the blackness of the opening, but that black 
velvet seemed to be nearly of the same intensity ; so that, pro- 
bably, when the luminous surface of the sun sends us 1000, 
.and the flats 469 rays, the solid surface seen in the openings 
reflects no more than about seven. 
.See Phil. Trans, for 1.800. p. 528, 
