MOUNT WILSON SOLAR OBSERVATORY. 293 



(76) In the green region of the iron are spectrum the distribution of 

 energy along the axis of the arc has been determined for Hues of groups 

 a and e. 



(77) The reflecting power of stellite is distinctly superior to that of 

 speculum metal over the range XX 3200-5800. 



(78) The remodehng of the 60-foot tower telescope and 30-foot 

 spectrograph has been finished and a new 13-foot spectroheliograph has 

 been built for use with the telescope. A 20,000 volt direct-current plant 

 and complete laboratory equipment have been provided for the study 

 of the Stark effect. The large Koch registering microphotometer has 

 been completed, and the ruling-machine is now ready for the first trials 

 in ruling gratings. Work on the larger parts of the 100-inch telescope 

 mounting has been nearly finished at Fore River. The driving-clock 

 and many of the smaller parts have been built in our shop. The para- 

 bohzing of the 100-inch mirror is about 80 per cent complete and the 

 erection of the 100-foot dome on Mount Wilson is far advanced. The 

 Mount Wilson road has now been widened sufficiently to permit the 

 transportation of the largest parts of the telescope. 



