SCIENTIFIC NOTES. 139 



came under my notice on my return was a remarkable confirmation 

 of this discovery. The Surveyor General has erected at the Ob- 

 servatory, for the purpose of connecting two hill stations, in the 

 trigonometrical survey, with Sydney, a most valuable theodolite, 

 made, with all modern accuracy, by Mr. Simms. The instrument 

 stands on a pyramidal stone base about 10 feet high. Very great 

 care was bestowed upon the construction and proportions of this 

 pier, yet when the theodolite was placed upon it and adjusted, an 

 unexpected difficulty presented itself — if the beautiful levels upon 

 it were adjusted with every care, a very short time sufficed to put 

 them wrong again, much to Mr. Surveyor Conder's annoyance. I 

 saw the changes going on, and at first thought the pier and instru- 

 ment had not settled down to a position of rest ; but, while looking 

 to see if this was so, I observed the sun shining on one side of the 

 pier. At once the discovery at the Edinburgh Observatory oc- 

 curred to me, and upon watching the pier it was found to obey the 

 same law. If the temperature increased on one side that ex- 

 panded, and vice versa. While upon transit circles, or the deter- 

 mination of accurate star positions in the meridian, I may mention 

 a remarkable invention of Father Resphigi, the King's Astronomer 

 at Rome, who showed it to me. Circumstances at his observatory 

 were favourable for this, though very unfavourable for astronomical 

 pursuits in many other respects. His observatory is on the top of 

 the Capitol at Rome, and it is so high that he was able by making 

 holes through various floors to place some mercury 100 feet below 

 a 4-inch transit instrument. Now, of all the tests applied to the 

 adjustment of the transit instrument, none is more satisfactory 

 than that of seeing the image of the lines in the eyepiece reflected 

 from a mercury surface, to prove that the line of sight is vertical. 

 If, then, a star could be seen at the same time, that star's posi- 

 tion would be known, free from the uncertainties that worry an 

 astronomer ; and owing to the distance of the mercury from the 

 instrument it is possible to see the star transit the wire, and at 

 the same time to see that the vertical adjustment is perfect. 



Some most valuable results had been thus obtained, when it was 

 found that even in Rome science had to give way to something 

 more practical. The Government wanted the lower floors for 

 offices, and shut up Father Resphigi's well and his investigation 

 together. 



Amidst all the improvements going on in the transit and other 

 instruments, the Equatorial is by no means forgotten, and though 

 I cannot enter into details of mechanical improvements, a few 

 facts about them may be mentioned. When in 1861 Messrs. 

 Chance Brothers exhibited a pair of discs over 25 inches in dia- 

 meter a wonderful stride had been made, and when after astrono- 

 mers and Societies had passed them by, Mr. Newall stepped in, 

 and, for the sake of science, bought them, and putting them into 



