4 
INTRODUCTION. 
parts of the world. The remainder of his life was devoted to the study of compara- 
tive geography and to literary pursuits. His first great work, the “ Bengal Atlas, 
containing Maps of the Theatre of War and Commerce on that side of Hindoostan,” 
was published in 1779, and a second edition in 1781/ This was followed by the first 
approximately correct Map of India, with a Memoir ' * I 2 containing a full account of the 
plan on which the map was executed and of his authorities. He conceived a great 
scheme for a comprehensive work on the geography of Eastern Asia, and published 
two volumes dealing with the geography of Herodotus. He also devoted much 
attention to the geography of Africa, and in 1790 constructed a new map of the 
northern half of that country for the African Association, accompanied by a Memoir. 
In 1791 he received the Copley Medal of the Royal .Society. The study of winds and 
ocean currents also occupied much of his time, and in 1810 he began to reduce his 
collection of observations to one general system. He was the first to explain the 
causes of the occasional northerly set to the southward of the Scilly Islands, which 
has since become known as c Rennell’s Current.’ On this subject he read two papers 
before the Royal Society in June 1795 and in April 1815. He was made an Asso- 
ciate of the Institute of France in 1800, and in 1825 received the Gold Medal of the 
Royal Society of Literature. He died on the 29th March, 1830, at the advanced age 
of 88, and was buried in the nave of Westminster Abbey. 
A few words may be added on the methods employed by Major Rennell in carry- 
ing out his surveys. The construction of scientific instruments had made very little 
progress when he was at work in India : indeed it was not until 1761, the year after 
Rennell went out, that the chronometer was first used for the determination of longi- 
tudes ; and his surveys were made with a compass and chain, supplemented by a 
Hadley’s Quadrant for the determination of latitudes. So badly equipped was the 
Government of those days in the matter of instruments that even in 1787 it was 
necessary to borrow a sextant, a watch, and a quadrant from different officers in 
Calcutta who happened to possess them, in order to fit out a Government Survey 
expedition for determining the positions of the principal places in Bengal. 3 Among 
the notes at the end of the Journal (p. 125) will be found measurements of the chain 
used by Rennell, from which it will be seen how inaccurate was even so simple an 
instrument. In spite of such disadvantages, however, his surveys were wonderfully 
accurate ; so much so that my friend Captain F. C. Hirst, of the Survey of India, 
while investigating the changes in the course of the river Kosi, found that many of 
the towns and villages marked in Rennell’s Bengal Atlas coincided exactly with their 
by reason of my Maims, & the ruined State of my Constitution ; unless my honourable Employers would 
generously assist me. 
I will not, Gentlemen, take up your Time with a Detail of my Misfortunes and Sufferings, as the Particulars are 
already well known to you : nor, as the hon ble Court of Directors have been pleased to approve of my Ser- 
vices, shall I plead the Merit of having done my Duty. 
I am with the greatest Respect, Gentlemen, Your most Obed .Servant, 
Fort William , 25 Ih Septv. 1774. J- REnnEW,, Surveyor-General. 
1 A reprint of this valuable work is now in course of preparation under the orders of the Surveyor General in India. 
2 Memoir of a Map of Hindoostan, or the Mogul Empire, &c., London, 1783. 
t Sir C. Markham, Memoir of the Indian Surveys, 2nd Edn., London, 1878, p. 56. 
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