XXVI PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



of the most affectionate regard, shows the esteem in which he was 

 held by his own countrymen. Those also, whose acquaintance with 

 him was less intimate, will feel the loss we have sustained in our social 

 intercourse, while the Society has lost an officer ever punctual and 

 exact in the performance of his duty. 



Major-General Thomas F. Colby, Royal Engineers, LL.D., 

 F.R.S.L. and E., F.R.A.S., M.R.I.A., died October 2nd, 1852, at 

 Liverpool, in the sixty-ninth year of his age. General Colby was the 

 son of Major Thomas Colby of the Royal jMarines, and grandson of 

 Mr. Colby of Rhosy-Gilwin m South Wales, a gentleman of consider- 

 able property. His maternal uncle was General Haddeu, Surveyor- 

 General of the Ordnance. He received his early education at North- 

 fleet School under Dr. Crockell, and was thence transferred to the 

 Royal Mihtary Academy, "Woolwich. At the early age of seventeen 

 years and three months, he received his first commission as a Lieu- 

 tenant of Royal Engineers, and only one month afterwards, in 

 January 1802, was appointed to the Trigonometrical Survey, on the 

 application of Captain jMudge of the Royal Artillery, then Superin- 

 tendent of that work. Though so young, he at once took part in all 

 the most important operations of the Survey; and when, in 1809, 

 Colonel ]\Iudge became Lieutenant-Governor of the R.M. Academy, 

 and was no longer able to give his undivided attention to the progress 

 of the work. Captain Colby performed all the duties of his executive 

 Officer, both in the Map Office and in the Observatory, with an 

 energy and ability which called forth from Colonel Mudge the 

 warmest expressions of gratitude and confidence. lu 1820, on the 

 death of General Mudge, Captain Colby succeeded him as Superin- 

 tendent of the Survey by the appointment of the Duke of Wellington, 

 who, on this occasion, took the wise precaution of obtaining the 

 opinions of the most eminent scientific men, including the President 

 of the Royal Society, on the fitness of Captain Colby to fill so import- 

 ant an office. In 1824 the superintendence of the Irish Survey was 

 also entrusted to him, and it was then that Major Colby invented and 

 had constructed the Compensation Bars for measuring the iriitial 

 base of that Surv^ey on the shore of Lough Foyle in the North of 

 Ireland. Similar bars constnicted also by Troughton, and on exactly 

 the same model, were afterwards used by Colonel Everest in the East 

 Indies to verify some of the old, and to measure new bases, whilst 

 the Irish bars were carried out to the Cape, and there used by 

 Maclear for measuring a base as the commencement of a new arc of 

 the meridian in S. Africa, so that Captain Colby's compensation bars 

 have alreadv been employed and found effective in three great geode- 

 sical operations. The arrangements of the Irish Survey were very dif- 

 ferent from those of the English work, as the object to be attained was 

 also widely different, namely to prepare maps of a scale sufficiently 

 large to become the basis of a Government valuation of land for local 

 taxation. General Colby for this purpose adopted the scale of 

 6 inches to a mile, and, following the example of Sir William Petty 

 in the celebrated Down Survey, proposed the employment of trained 



