ASTROPHYSICS IN THE UNITED STATES BOSLER. 369 



greatest beauty, show details of structure of wonderful delicacy. 

 Perhaps the most curious of these details are the dark streaks which 

 are apparent, more often than on the Lick plates, between the spi- 

 rals of a great number of the nebulae. The 60-inch telescope has 

 been in service but a short time, and we feel that there is no danger 

 in predicting that in the near future it will justify by new feats all 

 the hopes which have been placed upon it. 



But the founders of Mount Wilson wish to build yet greater 

 instrimients. A mirror of 2.54 meters diameter, which we had the 

 opportunity of seeing, is in the process of construction in the work- 

 shop at Pasadena. Meanwhile a new tower telescope, nearly 50 

 meters (150 feet) tall is nearly completed. This latter structure, 

 analogous to the one we have already described, will give at the 

 level of the ground a solar image 40 centimeters in diameter ; it will 

 be completed below by a well 24 meters deep containing the spectro- 

 scopes. Imagine what may be done with such apparatus ! Never- 

 theless, it is to be feared that the improvement of the image antici- 

 pated by Hale may be compromised by the vibrations of the coelostat 

 tower despite all the precautions to diminish them. 



We can not leave Mount Wilson without mentioning an extremely 

 interesting work which is also going on there ; one which has already 

 accomplished results of the first rank. We refer to the observatory 

 of the Smithsonian Institution which, under the direction of Mr. 

 Abbot, proposes to continue and extend the work of Langley upon 

 solar radiation. We can say that the results of these researches 

 represent our most accurate knowledge upon many of the most im- 

 portant details of solar physics; notably, the distribution of energy 

 in the solar spectrum, the absorption in the atmosphere, and the solar 

 constant of radiation. 



CONCLUSION. 



We have passed in review all the principal American observatories. 

 The more common American traits, you have without doubt re- 

 marked, are the extreme perfection of mechanical means, an ever- 

 watchful ingeniousness and the absence of all spirit of routine in 

 their constructions. We are speaking of the United States, where 

 everything in the daily life tends to develop practical ideas; and an 

 almost feverish activity turned unceasingly toward advancement is 

 noticeable in every profession. Meanwhile, we should not forget 

 that all these superb observatories, all these powerful instruments, 

 owe their existence to the enlightened and regal generosity of the 

 wealthy American men of industry. It is curious to note that these 

 men whose energy, at times hard hearted, has brought them success, 

 seem more attracted toward science than to those who have failed 

 97578°— SM 1910 24 



