5^8 PHILOSOPHICAL TRANSACTIONS. [aNNO 1742. 



Which converted into degrees of the equator, gives for the distance of the 

 same meridians 94° 50'. 



And several other observations gave nearly the same difference of longitude. 



The variation of the magnetical needle, or sea-compass, observed at Churchill 

 in 1725, as in N° 3Q3 of the Philosophical Transactions for the months of 

 March and April 1726, was at that time north 21° westerly, and this winter 

 Capt. M. carefully observed it at the same place, and found it no more than 

 J7°; so that it has differed about 1° in 4 years; for in 1738, he observed it 

 here, and found its declination 18° westerly. 



The Report of the Committee of the Royal Society appointed to examine some 

 Questions in Gunnery. N° 465, p. 172. 



Dr. Jurin having proposed 2 questions in gunnery to be examined, the Society 

 was pleased to appoint a committee for that purpose. The questions were, 

 1. Whether all the powder of the charge be fired, before the bullet is sensibly 

 moved from its place ? 2. Whether the distance to which the bullet is thrown, 

 may not become greater or less, by changing the form of the chamber, though 

 the charge of powder and all other circumstances continue unchanged ? 



At the meeting of the committee, it was proposed to divide the 1st question 

 into 2 parts. 1 . Whether all the powder of the charge be fired ? 2. Whe- 

 ther all the powder that is fired, be fired before the bullet is sensibly moved 

 from its place? 



As to the 1st part of the 1st question, the committee are of opinion, that all 

 the powder of the charge is not fired. And they found their opinion on the 

 following experiments: 



Pieces of paper used for hangings were laid close together on the ground, to 

 the breadth of 10 feet, in the line of a fowling-piece, between it and a frame 

 of 10 feet square, covered over with paper. On pointing the piece towards the 

 middle of the frame, and discharging it several times with and without ball, 

 some powder was always collected, but mixed with a great deal of dirt. 



It is however to be observed, that in 2 experiments made the 22d of July, 

 near the Artillery-ground, before the president and some of the fellows of the 

 Society, with a finer sort of powder, in a barrel of 3 feet 9 inches in length, 

 and 4- of an inch bore, with 12 dwts. of powder the 1st time, and 24 dwts. the 

 2d time, without ball or wadding, no powder could be found scattered on the 

 paper laid before the piece, nor sticking to a board at the distance of about 10 

 feet, against which the piece was pointed. But when the same powder was fired 

 in a short barrel of 5^ inches in the chace, either with or without ball, some 

 quantity of powder was always collected. 



