312 J. C. Watson—ZIntra-Mercurial Planets. 
ten degrees in breadth. He did not see any stars until he 
swept out to Mars and Regulus. 
Professor Hall told me that he had searched north of the 
sun, but that his assistant Mr. Wheeler had searched south. 
He said, however, that they had been compelled to use a very 
high magnifying power. Any one who has tried to find so 
bright an object as Jupiter by attempting to direct the tele- 
scope, with a high power, without using the finder, will know 
how uncertain a search would be under the circumstances 
named. 
As to what was done by other observers I have no direct 
information. Mr. Swift’s account of his work, as published in 
the New York Tribune, furnishes important corroborative evi- 
dence. But the records of my circles cannot be impeached by 
all the negative evidence in the world. There are no known 
ation +17° 80’ to +19°, I swept once forward and once back- 
ward, carefully, and I felt certain that the only objects besides 
stars, down to the seventh magnitude inclusive, were 
the two whose positions I recorded on my circles. I conducted 
the search expeditiously, but with great care, keeping the mo- 
tion of the telescope uniform; and if I were to repeat the 
observations I would not vary the method which I adopted nor 
undertake to examine a region of greater extent in the same 
period of time. I cannot conceive of asurer method of record- 
ing the position of an object observed, under the circumstances 
of these observations, without danger of mistake. 
Ann Arsor, Sept. 17, 1878. 
Since the letters of Sept. 8d and 5th were written, I have 
received information from Professor Newcomb, Commander 
Sampson, U.S.N., and Lieutenant Bowman, U.S.N., who were 
was no disturbance of their instruments at the time when these 
observations were made. I find, too, that the direction of the 
