Deoembeb 1, 1899.] 



KNOWLEDGE. 



275 



* Aegialitis curonica, Lesser Ringed Plover. — One only. 



* + Aegialitix caiitiana, Kentish Plover. — Abundant. 



* Squatarola helvetica, Grey Plover. — Abundant. Earliest date 



(bird), April 27. Seen on last day in marismas (May 19). 

 » t Vanellus vulgari.i. Lapwing. — Abundant. 



* t Seciirvirostra avoceila, Avocet. — Common. 



* t Simanfopus candidiis, Stilt. — Abundant. 



* Tringa a/pina,T>imym. — Common. Latest date (bird), May 14. 



* Tringa miniita. Little Stint. — Common. 



* Trinqa subarquata, Curlew Sandpiper. — Common. Seen on last 



day in viarismas (Mav 19). 



* Calidris arenaria, Sanderling. — Fairly common. Latest date 



(bird), May 15. 



* Machetes pugaa.r, Ruff. — Fairly common. Latest date (bird), 



May 3. 



* Totanus hi/poJeucus, Common Sandpiper. — Common. Seen on 



last day on river (May 23). 



* Totanus glareola. Wood Sandpiper. — A few. Earliest date 



(bird), April 12. Latest, April 25. 



* t Totanus calidris. Redshank. — Very abundant. 



* Limosa belgica, Black-tailed Godwit. — Several flocks. Large 



flock seen on last day in marismas (May 19). 



* Numenius arquata. Curlew. — Fairly common. 



* Numenius phreopus, Wliimbrel. — Fairly common. Latest date 



(bird), May 5. 



* t Sydrochelidon nigra. Black Tern. — Very common. Earliest 



dates — (bird), April 9 ; (eggsl, May 17. 



* t Sydrochelidon hybrids. Whiskered Tern. — Abundant. Earliest 



dates — (bird), April 9; (eggs), May 17. 



* Sterna anglica, Clull-billed Tern. —Fairly common. 



* t Sterna, minuta. Lesser Tern. — Common. Earliest dates — (bird), 



April 13 ; (eggs). May 18. 



* Larus ridibundi's. Black-beaded GuU.r-One only May 17. 

 Larus fuscus. Lesser Black-backed Gull. — Fairly common on 



sea coast. 

 Larus marinus, Great Black-backed Gull. — Faii-Iy common on 

 sea coast. 



* Larus gelastes, Slender-billed Gull. — Not common. 



HIPPALUS AND ITS SURROUNDINGS. 



By E. Waltek Maunder, f.b.a.s. 



THE district of the moon represented in our plate, 

 which is reproduced by the kind permission of 

 Messrs. Loewy and Puiseux from their magnificent 

 Atlas Photot/raphiijiii' de la Lime, is one of especial 

 interest. It shows us the region lying between 

 the Mare Nubium and the Mare Humorum, and presents a 

 great number of features which are of peculiar value in 

 determining the relative ages of the different types of 

 lunar formation. 



The more westerly of the two seas, the Mare Nubium, 

 is one of the larger of the great lunar plains, and only a 

 small portion of it is included in the plate, yet that is 

 sufficient to bring into prominence some of its most 

 characteristic features. Thus its surface is seen diversified 

 by numerous isolated ring-plains and broken by long 

 ridges ; whilst, as the photograph indicates with great clear- 

 ness, it is further marked by long light streaks. 



The most easterly sea, the Mare Humorum, is also only 

 shown in part, but though much smaller than the Mare 

 Nubium, the portion of it here seen is of great interest. 

 The Mare Humorum is one of the smallest of the lunar 

 seas, having an area about equal to that of England and 

 Wales. Like the Mare Crisium in the western quadrant, 

 to which it shows some features of resemblance, its 

 borders are, for the most part, distinctly marked. The 

 features, which in the photograph are the most striking, 

 though they are usually by no means easy objects in the 

 telescope, are the long ridges of sinuous form by which 

 the gradual descent from the mountain borders of the sea 

 to its lowest levels is broken up into terraces. 



Between the two seas stands the wrecked walled-plain 

 Hippalus, forming in its present condition a sort of bay or 

 extension of the Mare Humorum. A spur of hills con- 



tinues the rampart of Hippalus in the south-western 

 direction, and connects it with a very distinct ring-plain 

 Campanus, some thirty miles in diameter. The centre of 

 this spur of hills is marked by a bright crater, Campanus A, 

 which occupies as nearly as may be the centre of the plate. 

 Beyond Campanus to the south-west again is another ring- 

 plain, the twin of Campanus as to size and distinctness, 

 but distinguished from it by its level interior, whilst Cam- 

 panus shows a bright central peak and two crater pits, 

 both clearly marked in the photograph. 



Mercator and Campanus, and the mountains, which 

 prolong their general line of direction to the south-west, 

 divide the Mare Nubium from a small Mare, sometimes 

 described as the Sinus Epidemiarum. This plain would 

 be nearly rectangular in shape, and one hundred and eighty 

 miles long by one hundred miles broad, if it were not for 

 the invasion of a very striking ring-plain, seen in the 

 centre of the south-side of the plate, Capuanus. To the 

 east, the plain is bordered by a broad confused mountain 

 chain, whilst to the north-east, a bright mountainous 

 region, intersected by winding valleys, separates it from the 

 Mare Humorum. A very striking promontory projects from 

 this last mountain chain far out into the Mare Humorum, 

 three chief peaks of the promontory being lettered ag 

 belonging to the Hippalus region, Hippalus a, /i, and B. 



Proceeding north from Hippalus, the barrier between 

 the Maria Nubium and Humorum consists of a mountain 

 chain continuing in the same straight line the general 

 direction marked by Mercator, Campanus, and Hippalus. 

 This mountain region derives the names of its chief peaka 

 and craters from the irregularly shaped walled plain, 

 Agatharchides, on the north-west side of the range. 



The principal features of the remainmg part of the 

 margin of the Mare are the three contiguous formations on 

 the south-east. These are the two partially wrecked walled 

 plains, Doppelmayer and Lee, and a bright and strongly 

 ramparted ring-plain, Vitello. 



The chief portion therefore of the region represented in 

 the plate is lowland, and the various formations with which 

 the plains are diversified stand, for the most, in clear relief, 

 without confusion from crowding by neighbouring masses. 

 And, as the eleventh day of the month was well advanced 

 at the time the photograph was taken, the sun having just 

 risen on Doppelmayer, the sunlight throws up most of the 

 objects into the most favourable relief. 



Here, as everywhere along the margins of the great 

 plains, we are at once struck with the way in which the 

 matter composing the surface of the plain has attacked, 

 and more or less completely dissolved, the " seaward " 

 rampart, if we may use the expression, of the great walled 

 plains that border it. Hippalus, the fort that holds the 

 border line between the Sea of Clouds, and that of 

 Humours, is a conspicuous example. The south-eastern 

 wall has been destroyed, and the floor brought to the same 

 level as the invading plain. Lee and Doppelmayer on the 

 other side of the Mare Humorum have also suffered, 

 though less severely, and Capuanus on the Sinus Epidemi- 

 arum, though it has preserved the entire circle of its 

 rampart, yet shows the influence of the invasive matter, in 

 the way in which the western wall has sunk down ; the 

 entire formation seeming as if tilted over on its side 

 like a stranded boat. 



More striking still we have in the Mare Nubium two 

 examples of ring - plains, Kies and Lubiniezky, which 

 would appear to have sunk bodily in the invasive fluid ; so 

 low are their walls, and so complete the levelling of their 

 interiors with the surrounding plain. Yet, that it is not 

 always an essential that a ring should be overwhelmed by 

 the substance of the plain we can see in the great ring. 



