1881.] Dr J. B. Pearson, On Sympathetic Needles. 99 



matician of the first half of the seventeenth century, who also wrote 

 on the compass, and on the micrometer, or an instrument which 

 he calls by that name. He is said to describe Strada's imaginary 

 dials pretty literally, only giving names, Jean and Claude, to the 

 supposed friends: he does not seem however to have been at all 

 taken in, as he adds, "It is a fine invention, but I do not think 

 there is a magnet in the world which has such a virtue; besides it 

 is inexpedient, for treasons would be too frequent and too much 

 protected." Henrion's article is said to be illustrated with a dial 

 inscribed with the letters of the Alphabet and furnished with a 

 needle as an index, the needle turning on a pivot in the centre: 

 but the book is not in the Cambridge Library, or the Bodleian 

 Catalogue. Though the correspondent of Notes and Queries cites 

 from an edition of 1662, it appears from the Biographie Universelle 

 that the book was published as soon as 1627: and this explains 

 who is the author who is referred to by a German, Schwentner, 

 in a work called Delicice Physico-mathematicce, published in 1636, 

 and referred to in Notes and Queries, 2nd Ser. Vol. iv. 461: where 

 the same description recurs, the names being given as Claudius and 

 Johannes, which virtually proves that he borrowed from Henrion. 



Sir T. Browne, in his Vulgar Errors, Bk. II. c. 3, 16-19, again 

 brings up the notion, and says that he had experimented on it by 

 " framing two circles of wood, on which he placed two stiles or 

 needles composed of the same steel, touched with the same load- 

 stone, and at the same point." He candidly adds, as may be 

 expected, that no motion of any kind followed ; he admits however 

 that with a somewhat similar experiment he had a qualified 

 success, the description of which I give, because I am not sure 

 that I quite understand his method, and because those who are in 

 the habit of using magnets may like to repeat it. He says, after 

 referring to certain authors who " deliver many ways to communi- 

 cate thoughts at a distance ;"..." this we will not deny may in some 

 manner be effected by the loadstone ; that is, from one room into 

 another ; by placing a table in the wall common to both, and 

 writing thereon the same letters one against another : for upon the 

 approach of a vigorous loadstone unto a letter on this side, the 

 needle will move unto the same on the other. But this is a very 

 different way from ours at present : and hereof there are many 

 ways delivered, and more may be discovered which contradict not 

 the rule of its operations." Not long after Browne, Glanvill, in his 

 Vanity of Dogmatizing (1661), p. 204, refers again to the idea, and 

 criticizes the sufficiency of the test applied by Browne on grounds 

 that, as far as I can see, only prove that he had never read 

 carefully what Browne says : whose general meaning to me is clear 

 and rational enough. Glanvill is well known in the history of 

 that time as an original thinker, and as one of the earliest pro- 



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