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Dear Sir, Mr. Robert Douglas's observations of the variation, taken by himself, and signed by Dr. Halley, I now beg leave to return, with answers to the questions you proposed thereupon;viz . Whether I had ever seen them; or had made any use of them in my former publications? And if so, whether any further notice of them was necessary? In answer to the first; among my papers on the variation I have an exact copy of them, recommended under the same signature, of the same date, and in the same words, and the whole seems written by the same hand; so that both of them (containing 1719 observations each) may be stiled originals: I have sent mine herewith for your inspection. To your second question, I answer, that I could not make any use of them in the construction of either of my charts, as the first was formed from actual observations made about the year 1744, and Douglas's conclude in the year 1735; but as many of them as suited the periodic times were taken in, and compared with many thousands of others, according to the order of their respective dates, in forming the six periodic reviews, as published in the philosophical Transactions, vol. L. part I. for 1757. To the third question;viz . whether they are worth a public record? I rather think they are; and have sometimes thought to present them to the Royal Society for their approbation: for, not withstanding they have been thus made use of, yet they are mixed and moulded up with others, and those only to every five degrees of latitude and longitude; so that the variations respecting the several latitudes and longitudes do not singly appear.

philosophical transactions of the royal society of london

II. The variations of the compass; containing 1719 observations to, in, and from, the East Indies, Guinea, West Indies, and Mediterranean, with the latitudes and longitudes at the time of observation