Some Observations, Made during the Last Three Years, of the Quantity of the Variation of the Magnetic Horizontal Needle to the Westward; By Mr. Geo. Graham, F. R. S. at His House in Fleetstreet, London

These Hints, from one who never saw a House on fire, will, 'tis hoped, be farther improved by those who have more Experience and Skill in these Affairs. II. Some Observations, made during the last three Years, of the Quantity of the Variation of the Magnetic Horizontal Needle to the Westward; by Mr. Geo. Graham, F.R.S. at his House in Fleetstreet, London. Read Apr. 21. 1748. | Date | Inclination | |----------|-------------| | March 26 | 17 = 6 | | March 29 | 17 = 0 | | March 18 | 17 = 10 | | March 21 | 17 = 10 | | April 22 | 17 = 15 | | May 4 | 17 = 18 | | May 14 | 17 = 20 | | May 16 | 17 = 15 | | Dec. 18 | 17 = 25+ | | Febr. 24 | 17 = 30 | | Dec. 19 | 17 = 40 | | Jan. 4 | 17 = 40— | The Inclination of the dipping Needle has been during the same time about $73\frac{1}{2}$ Degrees. N.B N. B. As the Variation of the Needle at London has not been regularly published from time to time in the Philosophical Transactions: It may not be improper to take notice here, that according to the best Observations extant, and which were made by Persons of great Skill and Exactness, the Needle at London declined to the Eastward $11^\circ 15'$ in the Year 1580. In 1657 there was no Variation, the Needle then pointing due North. In 1672 the Variation was observed by the late Dr. Halley $2^\circ 30'$ towards the West, and in 1692 $6^\circ 0'$. And towards the Beginning of the Year 1723, it was found by Mr. Graham, from the Medium of a vast Number of Observations, to be then $14^\circ 17'$ the same Way. So that, during the Course of 167 Years elapsed since the Year 1580, to the End of the last Year 1747, the magnetic Needle at London has moved to the Westward, $28^\circ 55'$. See before No. 148, and No. 383 of the Philosophical Transactions.