"On Saturday, May 13th, 1826, I went to London on the way to Dolcoath, and received four chronometers from the Royal Observatory, Greenwich. I travelled by Devonport and Falmouth to Camborne, where I arrived on May 20th and dined at the count-house dinner at the mine. I was accompanied by Ibbotson, who was engaged as a pupil, and intended for an engineer. On May 24th Whewell arrived, and we took a pendulum and clock down, and on the 30th commenced the observation of coincidences in earnest. This work, with the changing of the pendulums, and sundry short expeditions, occupied nearly three weeks. We had continued the computation of our observations at every possible interval. It is to be understood that we had one detached pendulum swinging in front of a clock pendulum above, and another similarly mounted below; and that the clocks were compared by chronometers compared above, carried down and compared, compared before leaving, and brought up and compared. The upper and lower pendulums had been interchanged. It was found now that the reliance on the steadiness of the chronometers was too great; and a new method was devised, in which for each series the chronometers should make four journeys and have four comparisons above and two below. This arrangement commenced on the 19th June and continued till the 20th. On the 26th we packed the lower instruments, intending to compare the pendulum directly with the upper one, and sent them up the shaft: when an inexplicable occurrence stopped all proceedings. The basket containing all the important instruments was brought up to the surface (in my presence) on fire; some of the instruments had fallen out with their cases burning. Whether a superstitious miner had intentionally fired it, or whether the snuff of a candle had been thrown into it, is not known. Our labour was now rendered useless. On the 28th I packed up what remained of instruments, left for Truro, and arrived at Bury on July 1st. During our stay in Cornwall I had attended a 'ticketing' or sale of ore at Camborne, and we had made expeditions to the N.W. Coast, to Portreath and Illogan, to Marazion and St Michael's Mount, and to Penzance and the Land's End. On July 3rd I saw Mr Cropley in Bury gaol, and went to Cambridge. On the 4th I was admitted A.M., and on the 5th was admitted Major Fellow.
"I had engaged with four pupils to go to Orléans in this Long Vacation: my brother William was also to go. One of my pupils, Dobbs, did not join: the other three were Tinkler, Ogilby, and Ibbotson. We left London on July 9th, and travelled by Brighton, Dieppe, Rouen, and Paris to Orléans. At Paris I saw Bouvard, Pouillet, Laplace and Arago. I had introductions from Mr Peacock, Mr South, Mr Herschel, Dr Young; and from Professor Sedgwick to an English resident, Mr Underwood. On the 19th I was established in the house of M. Lagarde, Protestant Minister. Here I received my pupils. On the 28th I commenced Italian with an Italian master: perhaps I might have done more prudently in adhering to French, for I made no great progress. On Aug. 2nd I saw a murderer guillotined in the Place Martroi. The principal investigations on my quires are—Investigations about pendulums, Calculus of Variations, Notes for the Figure of the Earth (Encyc. Metrop.) and commencement of the article, steam-engine machinery, &c. I picked up various French ballads, read various books, got copies of the Marseillaise (this I was obliged to obtain rather secretly, as the legitimist power under Charles X. was then at its height) and other music, and particulars of farm wages for Whewell and R. Jones. The summer was intensely hot, and I believe that the heat and the work in Dolcoath had weakened me a good deal. The family was the old clergyman, his wife, his daughter, and finally his son. We lived together very amicably. My brother lodged in a Café in the Place Martroi; the others in different families. I left Orléans on Sept. 30th for Paris. Here I attended the Institut, and was present at one of Ampère's Lectures. I arrived at Cambridge on Oct. 14th.
"On Oct. 16th Whewell mentioned to me that the Lucasian Professorship would be immediately vacated by Turton, and encouraged me to compete for it. Shortly afterwards Mr Higman mentioned the Professorship, and Joshua King (of Queens') spoke on the restriction which prevented College tutors or Assistant tutors from holding the office. About this time Mr Peacock rendered me a very important service. As the emolument of the Lucasian Professorship was only £99, and that of the Assistant Tutorship £150, I had determined to withdraw from the candidature. But Mr Peacock represented to me the advantage of position which would be gained by obtaining the Professorship (which I then instantly saw), and I continued to be a candidate. I wrote letters to the Heads of Colleges (the electors) and canvassed them personally. Only Dr Davy, the Master of Caius College, at once promised me his vote. Dr French, Master of Jesus College, was a candidate; and several of the Heads had promised him their votes. Mr Babbage, the third candidate, threatened legal proceedings, and Dr French withdrew. The course was now open for Mr Babbage and me.
"In the meetings of the Philosophical Society a new mode of proceeding was introduced this term. To enliven the meetings, private members were requested to give oral lectures. Mine was the second, I think, and I took for subject The Machinery of the Steam Engines in the Cornish mines, and especially of the Pumping Engines and Pumps. It made an excellent lecture: the subjects were at that time undescribed in books, and unknown to engineers in general out of Cornwall.
"My College lectures seem to have been, Oct. 21st to Dec. 14th to 31 Junior Sophs, Dec. 4th to 12th to 12 Senior Sophs. I assisted at the examinations of the Questionists. I had no private pupils. On Nov. 26th I communicated to the Cambridge Philosophical Society a Paper on the Theory of Pendulums, Balances, and Escapements: and I find applications of Babbage's symbolism to an escapement which I proposed. I have various investigations about the Earth, supposed to project at middle latitudes above the elliptical form. In November an account of the Dolcoath failure (by Whewell) was given to the Royal Society.
"At length on Dec. 7th, 1826, the election to the Lucasian Professorship took place: I was elected (I think unanimously) and admitted. I believe that this gave great satisfaction to the University in general. My uncle, Arthur Biddell, was in Cambridge on that evening, and was the first of my friends who heard of it. On the same page of my quires on which this is mentioned, there is a great list of apparatus to be constructed for Lucasian Lectures, notes of experiments with Atwood's Machine, &c. In December, correspondence with Dollond about prisms. I immediately issued a printed notice that I would give professorial lectures in the next Term.
"On Dec. 13th I have a letter from Mr Smith informing me of the dangerous illness (fever) which had attacked nearly every member of his family, Richarda worst of all. On Dec. 23rd I went to Bury. The affairs with Cropley had been settled by the sale of his property under execution, and my father did not lose much of his debt. But he had declined much in body and mind, and now had strange hallucinations.
"The commencement of 1827 found me in a better position (not in money but in prospects) than I had before stood in: yet it was far from satisfactory. I had resigned my Assistant Tutorship of £150 per annum together with the prospect of succeeding to a Tutorship, and gained only the Lucasian Professorship of £99 per annum. I had a great aversion to entering the Church: and my lay fellowship would expire in 7 years. My prospects in the law or other professions might have been good if I could have waited: but then I must have been in a state of starvation probably for many years, and marriage would have been out of the question: I much preferred a moderate income in no long time, and I am sure that in this I judged rightly for my happiness. I had now in some measure taken science as my line (though not irrevocably), and I thought it best to work it well, for a time at least, and wait for accidents.
"The acceptance of the Lucasian Professorship prevented me from being pressed by Sedgwick (who was Proctor this year) to take the office of moderator: which was a great relief to me. As Lucasian Professor I was ipso facto Member of the Board of Longitude. A stipend of £100 a year was attached to this, on condition of attending four meetings: but I had good reason (from intimations by South and other persons in London) for believing that this would not last long. The fortnightly notices of the meetings of the Board were given on Jan. 18th, Mar. 22nd, May 24th and Oct. 18th.
"On Jan. 2nd, 1827, I came from London to Bury. I found my father in a very declining state (the painful rheumatism of some years had changed to ulcerations of the legs, and he was otherwise helpless and had distressing hallucinations). On Jan. 8th I walked to Cambridge. At both places I was occupied in preparations for the Smith's Prize Examination and for lectures (for the latter I obtained at Bury gaol some numerical results about tread-mills).