156 
SIE DAVID BEEWSTEE AXD DE. J. H. GLADSTONE OX 
It may be well to state that the angular measurements from which these numbers 
were calculated, showed a proportion between the different lines almost identical with 
that represented in the drawings of Sir Dayid Bkewstee, and also in the map of 
M. Matthiessen of Altona, 
lAght reflected from the Moon. 
As the light of the moon is only that of the sun reflected from her surface, it might 
be anticipated that it would exhibit the same flxed lines ; and so indeed it does. The 
authors of this paper, like other observers*, have remarked this. Sir David Bkewstee 
saw distinctly the lines in the lunar spectrum from B to near H, and placed it on 
record that they were exactly the same as those in the solar spectrum. Dr. Glad- 
stone observed the same, but with him the prismatic image appeared to terminate 
at the less refrangible end, just on the C side of B, and at the more refrangible end it 
seemed to be suddenly cut off by the line H ; but whether this was precisely the case 
could not be determined by measurement, as there was not sufficient fight in the field 
of view at the extremities of the spectrum to see the cross-wires of the telescope. 
When the moon sank towards the horizon, the more refrangible rays were found to be 
partially absorbed, while the fines C and D became very strongly marked ; C 6 made its 
appearance in its proper position — as determined by angular measui'ement — and the 
band ^ came distinctly into view. 
It is worthy of remark, that there is nothing in the reflecting sui'face of the moon, or 
in her atmosphere (if she have any), which produces fresh bands of absorption in the 
solar light, at least as far as prismatic analysis has yet revealed. 
Many observers have remarked that there are parts of the prismatic image which give 
rise to different sensations of colour according to their intensity. Thus in the spectriun 
of direct sunlight a broad space appears yellow, while in that of diffused fight the same 
colour is sometimes restricted perhaps to the narrow bright band between D and D 2. the 
adjoining rays appearing orange on the one side, and green on the other. Striking illus- 
trations of this were obtained during the examinations of the spectrum afforded by moon- 
light. Sir David Bkewstee saw the green space extending a little beyond F; Dr. Glad- 
stone found the portion between G and H, which is usually rfolet, to be strictly analo- 
gous in colour to those “ lavender ” rays beyond H, which he was then studying ; imd 
another party, to whom he showed the lunar spectrum, remarked at once the abnormal 
colour of these rays, but designated them “grey,” and that without knowing that 
Sir John Heesciiel had applied the same term to the almost invisible extreme rays of 
the solar image. In like manner. Sir David Beewstee on one occasion in describing a 
spectrum of the western sky after sunset, adds the note, — “ There is a slight tinge ot 
blue close to F, but the general colour beyond it is violet 
* Eoi- Frauxhopeii’s observations see Gilbert’s Ann. vol. Ixxiv. p. 375, 
