152 Proceedings of Philosophical Societies. [Feb. 



to the Parliamentary Standard, by Lieut.-Col. William Lambton, 

 FRS. In this paper, Col. Lambton expressed his satisfaction, 

 on account of the uniformity thereby obtained, that the com- 

 missioners appointed to consider the subject of weights and 

 measures have adopted Mr. Bird's standard. In order to reduce 

 the above arc to this standard, the measurement of it deter- 

 mined by the brass scale must be multiplied by '0000018, and the 

 product, subtracted for the correction ; and that by Itamsden's 

 bar must be multiplied by -000007, the product being added for 

 the correction. Col. Lambton has just completed some measure- 

 ments, which, when the requisite calculations are made, he 

 purposes to submit to the Royal Society. He is proceeding with 

 his arc through Hindostan ; if Scindiah's country continue quiet, 

 a section of it will pass through Gwalior, his capital, and end at 

 Agra on the Jumnah. 



Jan. 16. — Some practical Observations on the Communication 

 and Concentration of the Magnetic Influence, by Mr. J. H. 

 Abraham, of Sheffield ; communicated by the President. This 

 paper was divided into three sections; the first being on the 

 depth to which magnetism penetrates. In this, the author 

 stated, as the result of a number of experiments with steel bars 

 of various dimensions, that magnetism does not penetrate deeper 

 than the l-20th of an inch ; and that bars of 1- 10th of an inch 

 thick are as powerful as those of greater thickness, the increase 

 of surface in the latter being taken into consideration. The 

 second section related to the communication of the magnetic 

 influence : in this, some minute directions were given for the 

 formation of magnets of the bar and horse-shoe kinds, both 

 simple and compound ; the construction of a very powerful 

 compound magnet in the author's possession was explained by 

 means of a drawing. It was stated that magnetism, like electri- 

 city, extends at once over the whole surface of the body exposed 

 to its influence. If an octagonal bar of steel be magnetized by 

 a stroke with a set of magnet-bars along one of its sides, each 

 side, at the same distance from the centre, will acquire the same 

 degree of magnetic power. In another respect, however, mag- 

 netism differs from electricity in a striking manner : if a charged 

 Leyden jar be brought into contact with one that is not charged, 

 the electric fluid will be immediately communicated to the latter, 

 and it will be divided between the two in an equal proportion ; 

 but one bar of steel being placed upon another, though the upper- 

 most become magnetized over its whole surface instantaneously 

 bv a single stroke with a set of magnets, vet the lower one did 

 not acquire sufficient magnetic power for the attraction even of 

 needle pointings, which are much finer than iron filings. It was 

 the observation of the magnetic action on these pointings, that 

 led the author to his invention for obviating the ill effects of dry 

 grinding, which the Society of Arts had crowned with their 

 gold medal. In the last section of the paper, some phsenomena 

 in polarity were described. The author has succeeded in giving 



