November, 1910. 



KNOWLEDGE. 



435 



Mount Lowe and the like, but finding that the 

 place where the least quivering, due to bad 

 definition, i.e.. steadiness of the image was here. 

 The\- also saw that they got out of the way of 

 dust, which will occasionalK' even come here 

 as the result of some sand storm, and of 

 ordinar\- fogs. Fogs, though, will arrive in the 

 storm\' season. 



The site was selected six years ago last June, and 

 the instruments shipped here. 



Since .\pril, 1904, observations have been carried on 

 more or less continuously. Professor George E. 

 Hale is director. He came from the Verkes Obser- 

 \'ator\-. where his chief work was solar ph^'sics. 

 He is a man about forty- 

 one or two years old. 

 a graduate of Boston 

 Institute of Technolog\-. 

 Ferdinand Ellerman. next 

 in charge, has had jiri\ate 

 tuition, and has been at 

 the work about eighteen 

 or nineteen \'ears. His 

 specialitv is solar work. 

 Others here of note are 

 Dr. Adams, Backus, and 

 the pln'sicist Dr. Gale. 

 They have their own 

 camp and offices — even 

 generate their own elec- 

 tricity by gasoline engine, 

 and pum[) up their own 

 water. 



The best time for obser- 

 vations is considered tn 

 be half-an-hour after sun- 

 rise, and for perhaps two 

 hours later, i.e., as long as 

 the definition holds good. 

 This ma\' run through the 



\v!n)le da\'. The programme is to make photo- 

 graphs of the sun with the spectroheliograph. This 

 is done by forming the image of the sun on a 

 spectroscope, which is so adapted as to enable one 



one would see it in a telescope. The spots, with the 

 dark nucleus and the granulation in the surface, are 

 all there. The photographs are almost instantaneous, 

 being made b\- a high-grade shutter passing before 

 the "plate in one one-thousandth of a second. One 

 picture is show n which shows the calcium lines: this 

 bv letting onl\- these lines through the slit. The 

 more pronounced waviness in parts is likewise 

 noted, .\gain one sees that the line which admits 

 the light of the sun for a given chemical travels 

 across the plate in such w ise as to get in the whole 

 surface of the sun. There is now a record of 

 d fift\- plates with this new 



over one hundred 

 instrument. 



.\ Vr 



to photograph an nnage of the sun m mono- 

 chromatic ra\-s of an\- desired wave length. The 

 light passes through a slit, then through an objective 

 which renders the rays parallel, then falls on a mirror, 

 and thence is sent through two great prisms which 

 form a spectrum. Thence it goes via an objective 

 and through a second slit which permits one to 

 select any particular line in the spectrum, and by 

 this means photographs can be taken which will 

 show the vapours over the sun's surface, corres- 

 ponding to calcium. h\-drogen, iron, magnesium and 

 the like. The photographs are the size of the image, 

 i.e.. six-and-a-half-inches. The negatives are then 

 developed and one sees some of these glasses. At 

 the centre is the round image, like a great fog spot 

 with a rather crusty, skin-like effect, due to clouds 

 passing over the surface. Such is a direct photograph 

 made by a very fast shutter. It shows the sun as 



One passes then into the 

 new laboratory : this is of 

 solid concrete work, and 

 w ith instruments all about. 

 The\- can take a photo- 

 graph twice a day, 

 different each time, and 

 never twice the same, 

 the sun changing so con- 

 stantly. Daily a photo- 

 heliograph is taken: 

 two or three calcium 

 plates, and one hydrogen 

 plate. This is the regular 

 programme. If the defini- 

 tion is good, so that they 

 can compare to advantage, 

 the\' photograph through 

 iron and other lines, 

 and there are special 

 sittings. The difference 

 between the calcium 

 and hydrogen is made 

 apparent. The results 

 then are deduced here 

 and published in scien- 

 tific publications or monographs. 



One has a peep into the professor's home — a series 

 of little offices and bedrooms off from one hall, and 

 all built in the mission style. Windows look out 

 into the tree tops, as at Kila Monasteries in Bul- 

 garia, and the aisle then terminates in a library 

 finished in dark hea\-\- woods, with a huge stone 

 chimnev at one side. Round the walls range the 

 open shelves of books, with other heav\- splendid 

 furnishings, and heavy desks on which to write. 

 One looks right off from the bluff into the great 

 valle\- here, twenty-six acres below, to the Institu- 

 tion. As yet thev are not troubled by visitors, 

 though thev fear the\- w ill have some day to enfence. 

 The buildings are pe'rmanent, but others are still to 

 come for the great five-inch reflecting telescope. 



Some of the stellar photographs shown here, they 

 remark, took four nights to expose. The Observatorj- 

 is connected with the Carnegie Institute and so there 

 is no fixed sum allotted it. One year they got 

 S150,000 for maintenance. 



