Skptembeb 1, 1898.] 



KNOWLEDGE. 



175 



Aehernar — a name, in my opinion, which it should still 

 retain. 



I may here point out an erratum in the B. A. C, which 

 has not, I think, been noticed before. It ailixes the 

 letter a not only to Aehernar but also to a star of the 

 fourth magnitude, numbered 12 m Flamsteed's list of the 

 stars in Eridanus. The source of this mistake can be 

 traced ; it evidently arises from the circumstance that that 

 star is called a Fornacis by Lacaille. 



Yours faithfully, 



Blackheath, August 16th, 1893. W. T. Lynn. 



P.S. — In my letter to you of the 18th July (printed in 

 the last number, p. 1.51), the Greek word ka-ria, corre- 

 sponding to the Latin fm-us, is advertently spelt with the 

 smooth breathing. If a word were coined from it similar 

 to "perihelion," it would be " perihestian," but there 

 would be many objections to such a word. Mythologically, 

 'EcrTia corresponds to the Latin resta ; and, moreover, it 

 has never been used in a mathematical sense, like focus, 

 which (as I pointed out in my "Celestial Motions") is a 

 term transferred from optics to mathematics and astro- 

 nomy. " Perigee " (which surely should be "perigeen") 

 and " perihelion " are too firmly imbedded in astronomical 

 books now to be displaced, and there seems no objection 

 to the more recent " periastron." But, as Mr. Holt points 

 out, this is not the case with some of the hybrid words 

 used in reference to the planets. " Perijove " (if such a 

 word must be used) should be "perizena"; "perisaturnum," 

 in Gi-eek mythology, would be " perikronon." — W. T. L. 



To the Editor of Knowledge. 



SiK, — As it would appear from your August number, 

 containing some further reproductions of lunar photographs 

 by the skilful Brothers Henry, that the interesting and as 

 yet hardly-opened study of selenology is likely to continue 

 to occupy your pages a little longer, may I refer back to 

 your number for July last, and to that marvellous photo- 

 gravure of " the moon when 136 hours old," in order to 

 refer to some little points apparently not yet fully noticed, 

 and which perhaps would have passed unobserved by me 

 but for certain observations and photos made in Melbourne 

 some twenty years ago, when I was in charge of the great 

 telescope. 



At this distance in time and space my notes are not 

 available to refer to, but certain appearances have remained 

 indelibly impressed upon my mind, awakened as it then 

 was to the importance of selenology, as furnishing analogies 

 highly useful in the study of our own geology. 



In your article on "The Great Plains on the Moon" 

 (July), you remark upon " a curious, narrow, dark line 

 which seems not to be due to any photographic defect. It 

 skirts the high ground on the edge of the Mare (Tranquil- 

 litatis) for a distance of more than one hundred miles, and 

 ultimately seems to pass through or over a ridge to the 

 south of Sabine (65)." You then point out another similar 

 but broader line, " skirting the western edge of the Mare 

 Nectaris." The first of these (permit me for convenience"' 

 to call it Eanyard a) I remember to have seen, and on 

 the photo-plate it is to my eye undoubtedly an imperfectly 

 filled fault or fissure in the substance of the plain, the 



* While tliauking Mr. Mai^george for his kindly-inteuded compli- 

 ment, I trust he will permit me to change the proposed names in the 

 remainder of his letter to Tranquillitatis a and Nectaris 6, names 

 which seem to me to be decidedly preferable, because they roughly 

 indicate the position of these eui-ious markings, and because it does 

 not seem to me to be desirable to name portions of the moon or 

 planets after living people. — A. C. B. 



date being probably subsequent to the formation of Sabine 

 (65), the southern buttress of whose crater-wall it cuts 

 and breaks down in its course. Less distinct, but appa- 

 rently a similar formation, is that on the west of the Mare 

 Nectaris (Eanyard //), which to my eye seems terminated 

 by a minute craterlet, into which several branching creases 

 of the surface also dip and disappear. 



You have already observed that such small craters are 

 probably on the line of unseen faults in the lunar crust, 

 since they have a tendency to occur in strings or lines. 

 Your surmise is doubtless correct, since I have seen, in 

 the four-feet reflector, these two things in plain visual 

 connection. And even in the Henry photographs your 

 theory receives good support, since not only does Nectaris h 

 end in a craterlet, but Tranquillitatis a seems to terminate 

 also in the direction of a well-marked small crater east of 

 Sabine (65) ; while a southern parallel fault, branching from 

 Tranquillitatis a at mid-length, not only cuts but dislocates 

 to the east considerably the southern buttress of Sabine, 

 at a few miles distance, and then disappears towards a low 

 crater in the shadow of the other side. The effect of this 

 whole duplicated fault and dislocation is not only to bear 

 out your view, but, when coupled with the roller-like 

 undulations of the Mare advancing upon Sabine and Arago 

 (63), to give the impression of an extensive disruptive flow 

 of the lava-plateau towards the east, and which had found 

 its southern limit here. 



Before leaving this interesting rill, it may be observed 

 that Tranquillitatis a, at its western end, also disappears in 

 a craterlet, which may be seen at the northern termination 

 of the mountain ranges forming the buttresses of Hypatia 

 (317) ; but not before leaving, as a depression in its very 

 bed, a tiny craterlet, at a point a little to the east of where 

 a small pit with a whitish edge (probably also in connection 

 with this " fault ") nearly touches its northern edge. 



Nearly parallel with this rill and well on the other side 

 of Sabine will be found another fault, of older date than the 

 last, since it is almost effaced on the lower levels of the 

 plain, and entirely so where a low spur of Sabine cuts it 

 near its N.E. end. This fault ends in a well-marked 

 craterlet of very low ring-wall, on the plain between Sabine 

 and Manners (486). 



At its other extremity it gradually disappears amongst 

 the partially dislocated and small isolated ridge west of 

 the S.W. extremity of Tranquillitatis a. 



Northwards, and still upon the Mare Tranquillitatis, there 

 appears a curious scar, straight, and with its steepest edge 

 to the west, and situated on the plain nearly half-way 

 between Sabine and Maskelyne (67), which can hardly be 

 a photographic defect. It is even more distinct than the 

 little crater-pit a short distance further west, and it has a 

 curious parallelism with the meridional scars, creases, or 

 wrinkles which commence in the wall of Sabine and which 

 end somewhat convergently in or near Manners (486), 

 again supporting the theory as to faults and craters. It is 

 difficult to imagine these to be photographic defects, since 

 they appear also in the ring-wall of Sabine, both outside 

 and in, and take there a corresponding curvature. They 

 are probably rents produced by eruptive force in Sabine, 

 and consequently of later date. 



West of Arago (68), and in a line due north from 

 Theophilus, commences (again in some minute craterlets 

 or fumaroles) another fault, whose course has been almost 

 obliterated by subsequent fusion or degradation, but which 

 trends, with slightly curving south-westerly course, until it 

 ends in the low wall of Maskelyne (67), a half-sunk crater 

 of apparently older date. 



Turning further to the north, we may observe a curious 

 line bright lino, making as it were a continuation of tho 



