304 Notes on the Aspect of Mars in 1882. 
follow the process through all its initial stages, and gives the following description 
of it :-— 
“On the 13th January (1882), a very faint and ill-defined shade appeared to 
extend parallel to the Ganges; on the 18th and 19th these parts were covered 
with white spots and were no longer visible. On the 20th, | find it written that 
the Ganges appeared to be composed of two parallel lines, but the matter was 
doubtful, and not taken account of for that reason. On the 21st, the duplicity was 
evident, and so remained even on the 23rd of February. Similarly, the Euphrates 
was broad and dark on Jan. 19th, ill-defined and nebulous on the left hand side. 
On the 21st, there had already appeared, on the left hand side, a companion ‘ canal,’ 
and the Euphrates was the resultant of two equally broad and dark lines, each of 
which was indeed somewhat less intense than the single line of Jan. 19th. A 
similar nebulosity appeared to precede the duplication of the Canal of the Titans 
and the Pyriphlegethon.” 
These results are foreshadowings of what may be expected if it shall ever be 
practicable to employ the whole optical power and perfection of definition of the 
many large telescopes now in existence in studying the planet under favourable 
conditions. How rare such conditions are in our climate is, unfortunately, only 
too well known, no instrument of the class referred to having given more than 
momentary glimpses of those minute details which will require prolonged study 
in order to make further advance in knowledge of the constitution of this planet— 
details so minute and complex that the smallest tremor of the image suffices to 
confuse and render them undecipherable. 
During my observations, the power of 600 was generally used whenever the 
state of the air would admit of it. Professor Schiaparelli employed a power of 417, 
with an achromatic of 8°9 inches aperture. 
NovTEs ADDED IN PREss. 
Longitudes of the central meridian of Mars with the corresponding diameters of 
the disc at the epochs of some of the sketches and notes referred to in the preceding 
paper. Greenwich mean time throughout. 
Epoch. Longitude (A), Diameter, 
1882—Feb.,, . 1510 5 185-5 10-44 
March, . 7 8 34 336°5 8°66 
ee: 9 18 347°2 8°65 
mo dk@ Alt Le) 357°4 8°41 
o> o ii 8 oO 302°7 8°36 
o o 1B 8 40 281°4 8°22 
Ayal, 5 ib) 10 80 358°7 6°39 
