134 



KNOWLEDGE. 



[June 1, 1896. 



with the greatest care and patience, and his work is 

 still of much service in elucidating disputed points in 

 selenography. 



Schroeter's study of the moon practically ended with 

 the eighteenth century, and nearly twenty-five years 

 passed before another marked advance in selenography 

 took place. W. G. Lohrmann, of Dresden, was the next 

 to take up the work, and he commenced the construction 

 of an accurate chart thirty-seven and a half inches in 

 diameter. Like flayer, he was not destined to finish it. 

 A smaller map was issued just before his death, and a 

 larger one was published in 187''^, under the editorship of 

 the great selenographer, Schmidt. A contemporary of 

 Lohrmann was Gruithuisen, like him, a draughtsman of 

 great excellence, of whose drawings, published some years 

 ago, no less an authority than Klein has expressed himself 

 in terms of highest praise. 



The years 1836-37 marked an epoch in lunar science, 

 for they witnessed the publication of Beer and Miidler's 

 great map and text-book on the moon. The chart, thirty- 

 seven and a half inches in diameter, is still esteemed an 

 authority, and the monograph sufficed to settle for many 

 years the problem of active forces at work upon the surface 

 of the moon. Besides their great chart. Beer and Madler 

 issued a smaller one, which for beauty, accuracy and 

 moderate price, deserves much wider recognition than it 

 appears to have received, at any rate in this country. 



Once more a lull occurred in the advance of lunar science, 

 till at length the rapid increase in the power and excellence 

 of telescopes again forced the question of lunar change to 

 the front. Selenography, so long neglected in England, 

 was quickened by the action of the British Association, 

 which appointed a committee to investigate the matter and 

 to collect material for an adequate chart of the moon. It 

 was decided by the committee to draw up an outline map 

 two hundred inches in diameter. A portion of the work 

 had been completed when, for some reason or another, the 

 committee was dissolved. That enthusiastic student, the 

 late Mr. Birt, attempted to carry forward the work, which 

 was also helped on by the Seleuographical Society ; but 

 the latter, in its turn, to the great and permanent loss of 

 lunar science, succumbed after an all too short existence. 

 IsLore recently the Liverpool Astronomical Society, and 

 (in especial) the British Astronomical Association, have 

 accumulated much material of value, thanks in the main 

 to the labours of Mr. Thomas Gwyn Elger, one of the most 

 honoured names in the English annals of selenography. 



Before leaving our own countrymen, mention must be 

 made of the labom-s of Phillips, and of the text-books of 

 Nasmyth, Proctor, and Neison (now Xevill, Government 

 Astronomer at Natal). Nasmyth's elaborately illustrated 

 monograph is based on a series of finely executed models 

 of the lunar surface, which, for general eflect, have never 

 been surpassed. Proctor's handbook is noteworthy for the 

 skill displayed in handling the mathematical aspect of our 

 satellite. Nelson's great work, with its outline map, is 

 a monument of patient labour, badly in need, after nineteen 

 years, of a second and revised edition. 



We have seen what selenography owes to German 

 students, nor have we yet exhausted the Ust, for there 

 remains to notice the great chart of Julius Schmidt, six 

 feet in diameter, the labour of thirty years, and containing 

 no fewer than thirty-three thousand objects. This masterly 

 production, given to the world in 1877, represents the 

 furthest complete advanie in lunar cartography, but the 

 time is soon coming when a much larger and more 

 elaborate map will be required to keep pace with the 

 progress of observation. To the bulk of amateurs the 

 price of Schmidt's chart renders it inaccessible. Nelson's 



is, however, an excellent substitute, and smaller but very 

 perfect maps are those of Madler (already mentioned), 

 Mons. Gaudibert (a very fine production). Prebendary 

 Webb (in his " Celestial Objects," with its charming 

 description of the moon), and Mr. T. K. Mellor. Mr. Elger 

 also has just issued a map and handbook, which are 

 of the greatest possible interest and value. 



So far we have dealt with drawings and charts of the 

 moon ; we have merely mentioned the elaborate models of 

 Nasmyth, and have said nothing of such paintings as 

 those of Harrison and others. But space demands that 

 we pass to what bids fair to revolutionize the art of lunar 

 delineation, and to greatly advance our knowledge of the 

 constitution of the moon, if not to unlock its long-hidden 

 secret. When, in ISiO, the distinguished American 

 scientist, Dr. John William Draper, secured the first 

 photograph of the moon, he little thought what splendid 

 triumphs the sensitive plate would achieve in the ensuing 

 half century, or that the chemical image would far outrun 

 the most skilful fingers in depicting the intricate scenery 

 of the lunar surface. The earlier moon photographs were 

 small and comparatively uninteresting, but increased 

 attention was given to the subject, and in the sixties 

 Dr. Rutherfurd, of New York — to mention but one worker 

 out of many — achieved very noteworthy results. It was 

 soon found that, by enlarging these photographs, consider- 

 able detail could be made out ; but not until the great 

 reflector on Mount Hamilton was turned upon the moon 

 were the possibilities in this direction fully realized. 



In 1888, Prof. Burnham was placed in charge of the 

 photographic work of the great thirty-six inch telescope, 

 and secured a number of negatives of unsurpassed excellence 

 and beauty. In 1890 the work was renewed by Dr. Holden 

 and others, with the object of securing a series of 

 photographs so complete as to cover the whole history of 

 a lunation, and to include photographs made at various 

 critical stages of libration. It was soon found ( Dr. Holden 

 tells us*) that the Lick negatives " contained a wealth of 

 detail quite unknown in previous work of the kind, and 

 that they were admirably suited to provide the data for a 

 new study of the moon's topography." It was impossible 

 to examine the negatives properly at Mount Hamilton, and 

 negotiations were, therefore, opened with Prof. Ladislas 

 Weinek, director of the Imperial and Royal Observatory of 

 Prague, an astronomer of great experience and an exquisite 

 draughtsman. 



Sets of Lick photographs were placed at Dr. Weiuek's 

 disposal, and he tells us minutely in the Mount Hamilton 

 " Publications " how he proceeded with the work. Mean- 

 while experiments in enlarging had been made at the 

 Lick Observatory, both directly in the telescope and also by 

 subsequent exposure in the camera. The former were not 

 particularly successful. The latter showed that enlarge- 

 ment lip to a scale of three feet to the moon's diameter, 

 and even more, was perfectly feasible. Such photographic 

 enlargements were also made elsewhere ; amongst others 

 by Baron Rothschild, of Vienna, Jlons. Nielsen, of 

 Copenhagen, and Mons. Prinz, of Brussels. 



Dr. Weinek, when he commenced his work on the 

 Mount Hamilton negatives, was dissatisfied with these 

 photographic enlargements, and determined to turn his 

 great skill as a draughtsman to account by making 

 enlarged pencil drawings from the original photographs 

 examined by transmitted light under a magnifier. Equally 

 astonishing are the labour expended and the beauty and 

 accuracy of the results, the enlargements being the most 

 graphic and correct representations of the lunar surface 



* Publications of the Lick Observatory, Vol. III., 1894. 



