"The Harton Colliery Experiment: I had long wished to repeat the experiment which I had attempted unsuccessfully in 1826 and 1828, of determining by pendulum-vibrations the measure of gravity at the bottom of a mine. Residing near Keswick this summer, and having the matter in my mind, I availed myself of an introduction from Dr Leitch to some gentlemen at South Shields, for inspection of the Harton Colliery. I judged that it would answer pretty well. I find that on Aug. 11th I wrote to Mr Anderson (lessee of the mine), and on the same day to the Admiralty requesting authority to employ a Greenwich Assistant, and requesting _£100_ for part payment of expenses. On August 16th the Admiralty assent. There were many preparations to be made, both personal and instrumental. My party consisted of Dunkin (Superintendant), Ellis, Criswick, Simmons, Pogson, and Rümker: I did not myself attend the detail of observations. The observations began on Oct. 2nd and ended on Oct. 21st: supplementary observations were subsequently made at Greenwich for examining the coefficient of temperature-correction. On Oct. 24th I gave a Lecture at South Shields on the whole operation. In 'Punch' of Nov. 18th there was an excellent semi-comic account of the experiment, which as I afterwards found was written by Mr Percival Leigh." Of private history: "On Jan. 18th I returned from Playford. From Mar. 10th to 13th I was at Deal, and visited Sir John Herschel at Hawkhurst.--From June 28th to Aug. 7th I was staying with my family at The Grange, in Borrowdale near Keswick: and also made an expedition to Penrith, Carlisle, Newcastle, Jarrow, &c.; and descended the Harton Pit.--In September and also in October I was at South Shields on the Harton Experiments.--From Dec. 14th to 18th I was at Cambridge, and on the 26th I went to Playford." The following letter, written in answer to a lady who had asked him to procure permission from Lord Rosse for her to observe with his telescope, is characteristic: ROYAL OBSERVATORY, GREENWICH. _1854, September 20_. DEAR MADAM, The state of things with regard to Lord Rosse's Telescope is this. If a night is fine, it is wanted for his use or for the use of professional astronomers. If it is not fine, it is of no use to anybody. Now considering this, and considering that the appropriation of the telescope on a fine night to any body but a technical astronomer is a misapplication of an enormous capital of money and intellect which is invested in this unique instrument--it is against my conscience to ask Lord Rosse to place it at the service of any person except an experienced astronomer. No introduction, I believe, is necessary for seeing it in the day-time. The instrument stands unenclosed in the Castle Demesne, to which strangers are admitted without question, I believe............... Faithfully yours, G.B. AIRY.