YOL. XLIV.j PHILOSOPHICAL TRANSACTIONS. 397 



tract a 2d ball, and that a third, and so on, till the stream become too weak to 

 produce an attraction sufficient to support a greater weight. 



Exper. 9. — Having hung a number of balls to each other, by applying the 

 first to the north pole of a magnet, on presenting the south of another magnet to 

 one of the middle balls ; all those below it will be deprived of the magnetic stream, 

 and instantly losing their power of attraction fall asunder: the ball to which the 

 magnet was applied will be attracted by it, aud ^11 the others will still remain 

 suspended. But if the north end of a magnet be presented, then the ball to 

 which it is applied will also drop. 



Exper. 10. — In a magnet unarmed, the magnetic stream is carried back on 

 all sides in curve lines to the contrary pole, as was seen in Exper. 1 ; but when 

 armour is applied to each pole, the magnetic matter is conducted to the feet of 

 the armour ; and a lifter being thus applied to the feet, the whole stream coming 

 out at one pole is carried back through it to the other ; by which means the 

 lifter is made to adhere to the feet of the armour with very great force. When 

 the lifter is thus in contact, the magnet seems externally to have lost the greatest 

 part of its force ; though in reality it never acted with more. If instead of the 

 lifter, we suspend a number of iron balls in contact, they will adhere together, 

 and hang like a bracelet between the two feet; the returning stream passing now 

 through them, as before through the lifter. Present the pole of a magnet, and 

 they instantly fall asunder. 



Prop. 3. — The immediate cause of magnetic repulsion, is the conflux and ac- 

 cumulation of the magnetic matter. 



It appeared in the 5 th Exper. that the same poles of 2 different magnets being 

 opposed to each other, there was a conflux and accumulation of the magnetic 

 matter ; and we find by experience that all magnetical bodies in a like situation 

 are in a state of repulsion. 



Exper. 1 1 . — Two small bars, the one hard, the other of a spring temper, 

 being both magnetical matter, were opposed to each other, south to south ; the 

 filings produced the same appearance of repulsion, as described in the 5 th ex- 

 periment ; then the bars being brought so near as to touch each other at the 

 same poles, the repulsion was instantly changed into attraction. 



On the Usefulness of Thermometers in Chem,ical Experiments; and concerning 

 the Principles on which the Thermometers now in Use have been Constructed % 

 with the Description and Uses of a Metalline Thermometer. Newly Invented 

 by Cromwell Mortimer, M.D., Sec. R.S. &c. p. 672. Jppendix to N° 484. 

 Chemistry, being the most extensive branch of experimental philosophy, has 

 furnished mankind with the greatest number of curious and useful discoveries : 

 for not only the art of separating metals from their ores, of which metals are 



