86 CARNEGIE INSTITUTION 



ing during the day. As will be seen from the details given below, 

 the day conditions were found to be excellent ; very much better 

 than at any station tested in the south. Following is a record of 

 tests made : 



Thursday, June 18. — The erection of the telescope was completed 

 this afternoon, but not in time to make any observations on the sun. 

 Tests were made on the stars during the earlier portions of the 

 night. The seeing was only fair, about 3. 



Friday, June ig. — No tests were made during the forenoon. 

 Tests made upon the sun during the afternoon showed the seeing 

 to be good until 5.30 p. m., when observations were discontinued. 



Saturday, June 20. — Tests were made on the sun at intervals from 

 about 8.30 in the morning until nearly 6 in the afternoon. The 

 seeing was fair in the morning, good in the early afternoon, and very 

 good between 4 and 5 o'clock in the afternoon. Even at 6 p. m. it was 

 nearly as good as the best day seeing we had at Cuyamaca. Very 

 little wind. 



Sunday, June 21. — Tests were made at frequent intervals through- 

 out the day, beginning at 6.20 a. m. During the forenoon a pro- 

 nounced sea breeze was blowing, the air had a chilly feeling, and 

 the seeing was bad. In the afternoon the wind had decreased to a 

 very light breeze, and the seeing was greatly improved. The sun 

 spots have today been undergoing rapid changes. Some of these 

 changes could be appreciated without difficulty or uncertainty after 

 an interval of only a few minutes. From 3 to 4 o'clock the seeing 

 was at its best. The granulations of the surface, the detail in the 

 spots — both in umbrae and penumbrae — were then very clear and 

 steady. The appearance at this time may best be described by say- 

 ing that the effect as to clearness, sharpness, and steadiness was 

 very like that of a print from a steel engraving. 



At 4.30 the seeing was not so good as between 3 and 4 o'clock, but 

 still the details in the umbrae and penumbrae of the spots, the fila- 

 mentary character of the umbrae and the granulations of the sun's 

 surface were very distinct, and the periods of steadiness lasted for 

 considerable intervals. Between 5.30 and 5.45 the seeing was not 

 so good as earlier in the afternoon. The image was somewhat less 

 steady, and occasionally considerably blurred. 



No observations were made at night. There was a light wind at 

 Martin's camp during the evening, probably less than 10 miles an 

 hour. 



