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already that there is a large sea-region to the north of Dawes 
Strait, not shown in my chart. There is also a sea running 
southwards out of Nasmyth Inlet into Dawes Continent ; and 
there are some reasons for believing that Nasmyth Inlet runs 
into Tycho Sea. 
The following points have been indicated by Dr. Terby of 
Louvain, with regard to the regions just mentioned, as 
likely to need correction in my chart of Mars. In the main I 
agree with him. 
1. As to the form of Tycho Sea and Delambre Sea. Is it 
probable, Dr. Terby asks, that those seas are as shown in my chart, 
or have they the extension indicated in the drawings of Knobel, 
Green, and others in 1871 and 1873? In other words, is Rosse 
Land a permanent isthmus, or was the light streak seen there 
by Dawes only owing to a passing cloud ? I have already shown 
why I think the latter view the more probable. 
2. What are the relations between the seas of Tycho and 
Nasmyth Inlet, Beer Sea, &c. ? 
3. The exact configuration of the two dark bands which con- 
nect the seas of Tycho and Delambre with regions further west, 
requires to be determined ; may they not be simply the prolon- 
gations of those two seas, which in reality only meet on the 
eastern side ? 
4. What is the exact form of the faint prolongation of 
Tycho Sea towards the east, and what are its relations with 
Airy Sea. 
5. To verify the solution of continuity between Tycho Sea 
and this faint prolongation. 
6. To verify the existence of Lassell Sea and Leverrier Sea, 
of which no certain traces can be perceived in any drawings 
except those by Mr. Dawes. 
7. To study the polar sea of Schroter. 
8. To study the white region which Knobel and Green per- 
ceived immediately to the right of the Sea of Tycho. 
He gives a similar series of questions relating to six principal 
line series of the planet’s surface. I do not quote all his ques- 
tions for want of space. The above series will indicate their 
general nature ; the observer of Mars who notes with care the 
various and often varying features of the chief regions of the 
planet, should forward his pictures or tracings of them either to 
Dr. Terby, of Louvain, or to the Astronomical Society. It would 
be desirable to classify them in the way suggested by Dr. Terby, 
viz., with reference to the following six regions: — 
1. Kaiser Sea and Dawes Ocean, with their chief dependent 
features, extending between 30° and 1 20° of areographic longi- 
tude in my chart. (In Marth’s ephemeris published in the 
