Dr. Wollaston on the Magnetism of Metallic Titanium. 15 



Half of this l°-77 should be the amount of ascent, which 

 does not differ much from the experiment — a degree or a 

 decree and a half. The difference is also on the right side; 

 fo" we might easily conceive that the mercury is heated a little 

 as it comes down, and consequently does not sink so low as it 

 otherwise would, nor therefore afterwards rise so much. 



A like calculation for the second experiment would give 

 about 2°-4. This differs also from observation on the side 

 we might expect, but more than the preceding calculation. 



It is remarkable that if we take a number to 1-77 as -17 to 

 •197, it will be 1°'5, as nearly as possible that which was ob- 

 served in the first experiment ; and if we take a number to 

 2-4 as -17 to -197, it will be 2°-l, differing also but very little 

 from the second experiment. From this it appears that our 

 theoretical value is too high by about an eighth. Before, 

 however, much can be said with certainty, other and more 

 extensive experiments are wanting. But enough, I hope, has 

 been advanced, to show the danger of relying, in delicate ex- 

 periments, on the correction usually employed for that part 

 of the tube not immersed in the fluid. 

 London, Cranford, May 7, 1823. 



III. On the apparent Magnetism of Metallic Titanium. 

 By William Hyde Wollaston, M.D. V.P.B.S.* 



IN an account that I lately gave of the properties of metallic 

 titanium, which is printed in the First Part of the volume 

 of the Philosophical Transactions for the present yearf, diere 

 is an oversight, which I am desirous of rectifying as soon as 

 may be. I have there stated that the cubic crystals of ti- 

 tanium, when first detached from the iron-slag where they 

 are found, were all attracted by a magnet, but that when they 

 had been freed from all particles of iron adherent to them, 

 they appeared to be no longer acted upon by it. 



Having since that time been led, by the observations of 

 M. Peschier of Geneva, to examine this question more accu- 

 rately, I find that, although the crystals are not sufficiently 

 attractile to be wholly supported by the magnet, yet when a 

 crystal is supported by a fine thread, the force ot attraction 

 is sufficient to draw it about 20 degrees from the perpendi- 

 cular, and consequently that the force of attraction is equal 

 to about one-third the weight of the metal. 



When a piece of soft iron of about the same size was made 

 of a cubic form (weighing half a grain), the attractive force 

 * From the Philosophical Transactions for lS:2. - 5, Pare [I. 

 t Sec Phil. Mag. vol. Ixii. (>. 18. 



Of 



