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THE POPULAR SCIENCE MONTHLY. 



filled the valleys and covered up all the 

 mountains. The thickness must be regulated 

 by the quantity of snow falling, and this is 

 largest toward the coast, gradually diminish- 

 ing toward the interior. Hence the thick- 

 ness of the ice would be greatest on both 

 sides toward the coast, just as has been ob- 

 served. The surface of the snow-field in the 

 interior is even and as if polished, resem- 

 bling the undisturbed surface of a frozen 

 sea, the long but not high billows of which, 

 rolling from east to west, are not easily dis- 

 tinguishable to the eye. The principal factor 

 in giving the surface this shape is the wind. 

 A careful observation of a snow and ice cov- 

 ering like that of Greenland is of great im- 

 portance for the theory of the formation of 

 valleys and fiords. It seems that the more 

 we study Greenland, its coasts, and its inland 

 ice, the more convinced we must feel of the 

 power of the ice to perform this work. 



The Brnce Photographic Telescope. 



The Astronomical Observatory of Harvard 

 College has received from Miss C. W. Bruce a 

 gift of fifty thousand dollars for the construc- 

 tion of a photographic telescope such as the di- 

 rector had described in his circular of Novem- 

 ber 28, 1888, as desirable. The instrument 

 will have an objective of about twenty-four 

 inches aperture, and a focal length of about 

 eleven feet. It will differ from other large 

 telescopes in the construction of its object- 

 glass, which will be a compound lens of the 

 form used by photographers and known as 

 the portrait lens. The focal length of such 

 a lens is very small compared with its diame- 

 ter, and much fainter stars can be photo- 

 graphed in consequence. The advantage is 

 even greater in photographing nebulae or 

 other faint surfaces. Moreover, this form 

 of lens will enable each photographic plate 

 to cover an area several times as great as 

 that which is covered by an instrument of 

 the usual form. The time required to pho- 

 tograph the entire sky is reduced in the same 

 proportion. A telescope of the proposed 

 form, having an aperture of eight inches, 

 has been in constant use in Cambridge for 

 the last four years, and is now in Peru pho- 

 tographing the southern stars. It has proved 

 useful for a great variety of researches. 

 Stars have been photographed with it too 

 faint to be visible in the fifteen-inch refract- 



or of the observatory. Its short focal length 

 enables it to photograph as faint stars as 

 any which can be taken with an excellent 

 photographic telescope having an aperture 

 of thirteen inches. The eight-inch telescope 

 will photograph stars about two magnitudes 

 fainter than can be taken with a similar in- 

 strument having an aperture of four inches. 

 A corresponding advantage is expected from 

 the increase of the aperture to twenty-four 

 inches. Other advantages to be anticipated 

 from the use of such an instrument will 

 arise from the opportunities which the photo- 

 graphs will give for continuous and detailed 

 study. Witb them work can be done at any 

 place and any time, and, by multiplying 

 copies, by any number of observers. And 

 with them more could be added by a single 

 lens to our knowledge of the stars than could 

 be obtained by any number of telescopes of 

 the usual kind. Prof. Pickering is seeking 

 the best possible location at which to mount 

 the instrument. Owing to the difficulty in 

 maintaining regular observations in the East- 

 ern States that arise from the prevalence of 

 cloudiness, he suggests one of the mount- 

 ains of southern California as likely to offer 

 the most favorable climatic conditions at- 

 tainable. 



What it takes to play a Piece of Music. 



Science, says Sir James Paget, will sup- 

 ply the natural man with wonders uncount- 

 ed. The author had once heard Mile. Ja- 

 notha play a presto by Mendelssohn. She 

 played 5,595 notes in four minutes and three 

 seconds. Every one of these notes involved 

 certain movements of a finger, at least two, 

 and many of them involved an additional 

 movement laterally as well as those up and 

 down. They also involved repeated move- 

 ments of the wrists, elbows, and arms, alto- 

 gether probably not less than one move- 

 ment for each note. Therefore there were 

 three distinct movements for each note. As 

 there were twenty-four notes per second, 

 and each of these notes involved three dis- 

 tinct musical movements, that amounted to 

 seventy - two movements in each second. 

 Moreover, each of those notes was deter- 

 mined by the will to a chosen place, with a 

 certain force, at a certain time, and with a 

 certain duration. Therefore there were four 

 distinct qualities in each of the seventy-two 



