THE SOLAR SPECTRUM IN 1877-1878. 291 
glass, about as much more length still in that ultra violet direction; just as 
indeed, the fluorescent observers have already discovered with their peculiar 
apparatus. 
Wherefore what a result, we have hereby now obtained. Not free, I must 
confess, from innumerable little causes of discrepance, and uncertainty from varia- 
tion of details of instruments and modes of observing, between one spectroscopist 
and another ; but invested with a remarkable breadth of common-sense appre- 
ciation of a something all important, about what the public would call degrees 
of heat. And which, though not yet capable of being employed very positively 
for science itself, may at least and at once induce many scientific men to be 
more cautious in future as to what heating methods they should strive to employ, 
and be careful to define and record the temperature results thereby attained, 
whenever they compare spectroscopically, terrestrial! chemical elements in incan- 
descence, with the Solar elements in a similar condition. For, by how much the 
deflagrating temperatures of the most powerful electric sparks yet prepared by 
man, exceed the lower than freezing temperatures of the upper air,—by just 
about as much, and even a little more too, is the former exceeding high 
temperature surpassed by the almost unspeakably still higher temperature of 
the surface of the Sun, inch for inch, within its own domain. 
Parr III. 
Rit SOAR SPECTRUM ITSELF 
at the date 1877-1878. 
This is a complete spectrum from one end to the other of everything visible 
to the eye through glass lenses and prisms, under dispersion powers of 33° 
(A to H) at the red, down to 10° (A to H) at the violet or lavender end; 
and with magnifying powers of 10 to 20 on the telescope of inspection; the 
light being reflected to the slit occasionally by a silver-on-glass reflector, but 
more generally by a glass plate quick-silvered on the back. 
Hence this spectrum necessarily terminates a little beyond the H lines, and 
has no pretence of competing with metallic reflections, quartz lenses, fluorescent 
eye-pieces and photographic registrations, for their capacities in the more 
refrangible regions. It is simply an eye record of the luminous phenomena 
which are capable of being transmitted through glass. 
On the other hand it is peculiarly a spectrum of solar lines with the least 
possible ¢ellwtc admixture, as the observations were made at Lisbon, in June 
and July, and always near the middle of the day when the sun had an altitude 
of nearly 70°. It is also a peculiar record of solar spectrum colours, as direct 
