June 1, 1895.] 



KNOWLEDGE 



135 



that have ever been produced. When these enlargements 

 first appeared their revelations were received in many 

 quarters with incredulity, but close examination tends to 

 confirm their correctness and to render certain the existence 

 of the minutest details, not only in the photographs, but on 

 the moon itself. 



These magnificent hand enlargements, as we have seen, 

 cost Dr. Weinek immense labour. His study of Copernicus 

 alone occupied him two hundred and twenty-five hours. 

 The distinguished astronomer was then led, in conjunction 

 with Dr. Spitaler, to study closely the problem of 

 photographic enlargement, and has been fortunate enough 

 to discover a method (which for the present he reserves) 

 of greatly reducing the grain, the cnij- of the whole 

 problem of enlargement. The results achieved by the new 

 process are remarkable, especially when we study them as 

 applied to the moon photographs obtained at the Paris 

 Observatory by Messrs. Loewy and Puiseux of that estab- 

 lishment. These photographs are obtained with an 

 equatorial caude of eighteen metres (sixty feet) focus and 

 sixty centimetres (thirty-three and a half inches) aperture, 

 with an exposure of half a second. They are exquisite 

 productions, and superior, if that were possible, to the 

 Mount Hamilton photographs. Dr. Weinek has enlarged 

 portions of them to a scale of thirteen feet to the moon's 

 diameter, that is, double the scale of Schmidt's celebrated 

 chart. 



An examination of these enlargements shows, as was to 

 be expected, much detail not found on the finest maps, and 

 they will be of the highest value in the production of the 

 next great chart of the moon — a chart which will as much 

 surpass the classic map of Miidler as Madler's does the 

 quaint map of the old selenographer of Dantzic. 



[Dr. Weinek has very obligingly forwarded two of his 

 enlargements of portions of the moon, to illustrate Mr. 

 Mee's paper. The original photograph was taken by 

 the Brothers Henry on March 1-ith, 1894, at 6h. 38m. 57s., 

 Paris mean time, and the enlargements as made by 

 Dr. Weinek were on a scale of four metres to the lunar 

 diameter, a magnification of 23-36 times linear. In the 

 accompanying reproductions a scale of two and a half 

 metres to the lunar diameter has been employed, the 

 actual scale, therefore, being somewhat greater than 

 that of Schmidt's great map. The two regions repre- 

 sented are Albategnius and Maurolycus. Both are well 

 known as amongst the finest examples of lunar walled- 

 plains. The former was included in the photograph of 

 " Sunrise on Ptolemaus," published in the number of Know- 

 ledge for December, 1894, Albategnius and Ptolemaus 

 being neighbour formations. It is 64'G miles in diameter, 

 and is surrounded by a mountain wall of great height 

 and steepness, the loftier peaks of which have a height 

 of ten thousand feet or more. The principal new 

 marking discovered by Dr. Weinek in this region is a 

 crater pit about two miles in diameter, on the level floor 

 of Albategnius and S.W. of the central mountain, about 

 halfway from it towards the outer wall. The region of 

 Maurolycus has been much more fruitful in new objects, 

 some of which are indicated in the little sketch-map 

 subjoined. Amongst these, special attention may be drawn 

 to the chain of four crater-x^its just within the east wall of 

 Maurolycus, and a very distinct rill proceeding from a 

 newly-discovered crater-pit and crossing the outer southern 

 wall of the plain. Two new objects are also shown on 

 the tloQr of the ring-plain Barocius, from one of which a 

 rill proceeds in a N.E. direction. 



I should like to add just a few words to Mr. Mee's 

 admirable resume of the progress of selenography, and to 

 refer to by far the most complete collection of lunar 



photographs at present in existence, that taken under the 

 direction of the late Prof. Pritchard with the twelve- inch 

 De la Rue reflector at the Oxford University Observatory. 

 The photographs, which exceed one thousand in number. 



noO 



were taken for the purpose of measuring the lunar libra- 

 tion. Though from their small size — the image ol the 

 moon being scarcely more than an inch in diameter 

 — they cannot compare with the photographs taken 

 recently at Lick and at Paris, yet many of them show 

 much beauty of detail, and bear considerable enlarge- 

 ment. — E. Walter MAUNiU'E.] 



Hcttcrs. 



[The Editor tloes not hold himself responsible for tlie opinions or 

 statements of correspondents.] 



FLUCTUATIONS OF MIRA CETI. 



To the Editor of Knowledge. 



Sir, — The letter on Mira in the March number of 



Knowledge leads me to ask, what has been the experience 



of observers of that star this year on your side of the 



Atlantic '? 



The writer, working with a field-glass, has seen two 

 maxima and two minima of Mira, also two each of E Leonis, 

 during the past month, and a well-known astronomer, 

 who confirms these observations, saw similar fluctuations 

 of R Trianguli about the same time. 



The two first named are still visible — Mira as -l-S mag- 

 nitude and R Leonis as 5-3 magnitude. 



Yours faithfully, 

 Memphis, Tenn., U.S.A., Davto Flanery. 



15th March, 1895. 



[The following three letters from experienced observers 

 of variable stars on the point raised by Mr. David Flanery 

 do not directly confirm his observations ; though the 

 difference in the date of maximum as fixed by Herr Plass- 



