VOL. LXII.] PHILOSOPHICAL TRANSACTIONS. 36l 



Fourth set of experiments, viz. the same side of 72° 10' 



the instrument to the east, as in the first set of expe- 72 10 



riments. 72 15 



72 10 

 11 10 

 72 10 



Fifth experiment, viz. the same end of the needle made north, as in the 

 first set of experiments, and also the same side of the instrument to the west, 

 as in the first set of experiments, 72° 20'. 



Experiments made April 22, 1772, with the other 72° 15' 



dipping needle, the instrument being put in the same 72 10 



place, and with great care, in the magnetic meridian, 72 20 



the needle pointed as annexed. On the 2d of these, the poles of the needle 

 changed. And in the 3d, the side of the instrument to the east, which in the 

 first observation was to the west. 



Lest any thing magnetical should have affected the 72" lO' or 15' 



needle in Mr. Nairne's house, he took this instru- T% 20 



ment, and placed it in the middle of a large room 72 30 



belonging to the London Assurance in Birchin-lane, 72 10 



and then the needle pointed as annexed. At the 3d of these, the poles of the 

 needle changed. And at the 4tli, the side of the instrument to the east, which 

 in the first observation was to the west. 



The dipping needle brought back, to Mr. Nairne's, and put in the same place 

 as before, stood at 72° 10' +. 



In the foregoing experiments, the needle was raised to an horizontal position, 

 and left to vibrate. It was between 8 or Q minutes before the vibration ceased. 

 The needle brought to an horizontal position, and one grain and a half laid on 

 the extremity of the south end, was not sufficient to keep it in that position; but 

 the north end pointed to 35° 30'. One grain and three quarters laid on the 

 extremity of the south end of the needle, was more than sufficient to keep it in 

 the horizontal position, the south end then pointing 6° 45' below 0. 



END OP THE SIXTY-SECOND VOLUME OF THE ORIGINAL. 



T. Discovery of the Manner of making Isinglass in Russia ; with a particular 

 Description of its Manufacture in England, from the Produce of British 

 Fisheries. By Humph. Jackson * Esq., F.R.S. Anno \7JZ. Vol. LXUL p. 1. 



All authors, who have hitherto delivered processes for making ichthyocolla, 

 fish-glue or isinglass, have greatly mistaken both its constituent matter and pre- 

 voL. xm. 3 A 



