“Doubt” 7, p. 93. “For it is evident from experience that iron is so indisposed by some qualities that it cannot be moved by the magnet. That fishes swimming over the _Torpedo_, enclosed in the mud or sand for the purpose, when they come to the places whereto the virtue of the _Torpedo_ is extended can stir no further; by which art she catches and eats them, as Aristotle relates (6 ‘de Hist. Animal.,’ cap. 10; and 9 ‘de Hist.,’ cap. 37).” “Doubt” 7, p. 94. “For if amber be dulled by moisture, its virtue cannot produce motion in straws. If the virtue of the _Torpedo_ reach the fishes swimming over her, or the fisher’s arm their motive power cannot produce motion.” “Doubt” 7, p. 96. “And for this cause, the virtue of the magnet can produce motion in iron, not in other bodies, because it finds in it Dispositions necessary on the part of the agent which, being present, it can operate; not in other things. And, for the same reason, amber moves straws, not iron nor stones.” The preface to the “Arbor Vitæ ...” is written by Richard Browner M.L. Coll. Med., London, who translated out of Latin “The Cure of Old Age,” by Roger Bacon, wherein he gives quite a good account of the latter’s life and writings, and from which we extract but one passage likely here to be of some little interest, viz. at p. 155, regarding the component parts of a medicine: “By Amber here our author intends Amber Gryse (a bituminous body found floating on the sea): For he calls it Ambra and not Succinum (which is solid Amber). Besides, Succinum was never reckoned a spice as Amber is here. And though both Ambra and Succinum be great restorers of the animal spirits, yet the former is more efficacious.” The “Biographie Générale,” Vol. III. p. 348, says that Duarte Madeyra Arraess, who died at Lisbon in 1652, was the author also of “Apologia,” 1638, of “Methodo,” 1642, and of “Novæ Philosophiæ,” 1650. =A.D. 1683.=--Halley (Edmund), LL.D., who became English astronomer royal, makes known his theory of four magnetic poles and of the periodical movement of the magnetic line without declination. He states that the earth’s magnetism is caused by four poles of attraction, two of them being in each hemisphere near each pole of the earth. By the word _pole_ he means a point where the total magnetic force is a maximum, or, as he himself styles it, “a point of greatest attraction” (Walker, “Magnetism,” p. 317, etc.). One of the magnetic poles he places near the meridian of Land’s End, not above 7 degrees from the North Pole, the other being about 15 degrees from the North Pole in the meridian of California, while the two south magnetic poles are placed respectively about 16 and about 20 degrees from the South Pole of the earth, and 95 degrees west, 120 degrees east of London.