THE OBSERVATORY ON MOUNT WILSON, WHERE 

 MIRRORS SUPPLANT THE TELESCOPE TUBE. 



By FELIX J. KOCH. 



The reCL'iit appearance and disappearance of 

 Halle^•'s comet has thrown the star gazers into 

 the public eve, and among observatories none, 

 perhaps, has given rise to more comment than 

 the great Carnegie one t)n Mount \\'ilson. near 

 Los Angeles, California. This, perhaps, largely 

 because it is unique 



world's ob- 



among the 

 servatories. 



To reach Mount \\'ilson 

 from the end of the near- 

 est car line means a long 

 burro ride through the 

 mountains. There the 

 one peak of the twins 

 forming the summit is 



given 

 hotel, 



over to a rustic 

 and surrounding 



this, for indi\idual guest 

 rooms, are a series of 

 chalets, each a full-fledged 

 house to be occupied by 

 the guest. 



Entrenched in these 

 one proceeds through the 

 forest down into a gulch 

 and on to the opposite 

 mountain, where the great 

 Observatory connected 

 with the Carnegie Insti- 

 tute of Washington. D.C., 

 is established. 



The building, to begin 

 with, appears like some 



1 iie edue ot the Ark. 



hug 



It is of white 



canvas, immense, and in the shape of a barn. It 

 stands on the very tip of a mountain, surrounded 

 on all sides b\' open vallev. One surveys lower 

 forested peaks rising out of this valle_\', and the 

 flat plain leading off into the distance. The scene 

 is sufficient!},' magnificent to repav for the journey. 



Turning, there lie, basking in the sun, a large 

 white series of buildings set in perfect line on this 

 peak. 



A professor is at hand to guide you, and he leads 

 into the main building. This is built up of canvas, 

 set in eave form on the sides so as to admit plenty 

 of air. Then outside these canvas eaves there runs 

 another wall of canvas, such that it can be raised or 



lowered, and thus ensure the same temperature 

 inside the building as out. 



One looks at once for telescopes, but in \ain. .\ 

 series of mirrors appears instead, and it is the third 

 of these, you learn, which does the magnifying 

 instead of the usual tube telescope. You look 



into this mirror and see 

 enlarged the image of the 

 star or moon. In order 

 to get this, plainer still, 

 a pocket magnif^"ing glass 

 is brought into pla\-. The 

 arrangement is a unique 

 one for an observator\'. 



Nor is this all. The 

 tent in which this third 

 mirror stands is built 

 upon a track, so that it 

 may slide nearer to or 

 farther from the next 

 building, in which there 

 are two other mirrors, 

 while beyond is a little 

 shed in the canvas build- 

 ing, for star work and 

 for the spectrum instru- 

 ments. 



This telescope, the 

 guide narrates, is a twent\- 

 four inch one, made h\- 

 their own people, and 

 brought out from the 

 Yerkes Observatorw On 

 the end of the building 

 there is a pier of stone, 

 by twent\- long, which 

 a concave mirror of twenty-four inch 

 aperture h\ si.xtv foot focus. This was made 

 at the Yerkes Observatory. Any good optician, 

 however, could make one of these fine circular 

 mirrors. The concavitv is very great. The mirror, 

 as a matter of fact is four inches thick, and silvered 

 on the front surface. It takes about two months for 

 two men to make such a mirror. This is polished 

 by jewellers' rouge on pads of chamois skin. The 

 mirror is burnished every week or ten days to 

 remove the dust. It is then ke[)t covered over w ith 

 a galvanized cover. 



A second mirror is supported by a number of 



perhaps three feet wide 

 contains 



433 



