272 REPORT—1852. 
glasses on the spectrum indicates’ some peculiar influences, which require more 
extensive study than they have yet received. The remarkable difference 
between the luminous and the chemical spectrum is very striking, and it ap- 
pears to indicate the independent existence of the actinic or chemical rays. 
(66) 3. CoMBINATION BLUE AND GREEN (37), fig. 31.—The spectrum 
impressed by long exposure commences at -45 and terminates sharply at 1-0, 
there being no indication of any action beyond the visible spectrum. It will 
be found by examining the drawing of the luminous spectrum obtained 
when the light has passed this combination of Fig. 31. Fig. 32. 
glasses, that the action commences at the lower a 
edge of the green rays. ‘The whole space im- Dir’. as 
pressed has equal intensity throughout, with a 
brightening of the silver in the middle. 
(67) 49. A Licur BLUE (35), fig. 32..—The 
action commences at the lower edge of the blue 
rays ‘55 from 0, and extends to 1:40, when it is 
suddenly interrupted. Considering the usual 
character of blue glasses, and that this one is Ong 
an unusually transparent nature, it will be ue- 
cessary to subject it to a much more search- 
ing examination than it has yet veceived. That 
the chemical change is very superficial, is proved by the 
rapidity with which the hyposulphite of soda removes the 
impression. 
(68) 46. CopaLt-BLUE (36), fig. 33.—Action com- 
mencing at °75, extending with full euergy to 1°50; at 
the lower edge it is continued with faint shading to °55, 
and even some very slight continuation to ‘0, which is to 
be detected by placing the collodion glass plate upon a 
sheet of white paper and viewing it at a small angle, and 
shading off at the most refrangible end, until at 2°10 all 
action appears to cease. This is the greatest extension 
of the spectrum which up to this date (August 20, 1852) 
has been obtained; and in two experiments made in very 
intense sunshine at noon-day, a well-marked spot has 
been obtained °10 below 0, as marked in the drawing. 
This spot will be found to correspond with one of Sir 
John Herschel’s heat spots, and may possibly be referred 
to some peculiar chemical action due to the so-called pa- 
rathermic rays. The presence of vapour, in the form of 
light cloud or mist, however attenuated, appears to ob- 
struct this peculiar class of rays. 
(E.) Miscellaneous Series. 
(69) 101. SMOKY-COLOURED GLASS (46), fig. 34.— Che- 
mical action commences at “70 and extends to 1:90. At the 
least refrangible end the impression descends faintly to *50. 
The maximum of action is within the limits of the visible most 
refrangible rays, the most intense spot being near Fraunhofer's 
line H. 
Those media which have been employed in the analysis of 
the prismatic spectrum, and are described in the optical series, 
put which do not appear in the chemical one, have been omitted, 
until further experiments confirm, or the contrary, the results 
which have been obtained. a 


