Mr. Rutherford's Reply to Mr. Halliwell's Inquiry. 229 



increased by the insertion into 

 the spiral of a bundle of iron 

 wires, but, on the contrary, di- 

 minished by a bar of iron. The 

 thermic action is diminished in 

 both cases, but that of magne- 

 tizing steel increased ; the cur- 

 rent so induced behaves there- 

 fore exactly like that induced 

 in another wire. 



3. On the Magnetism of the so-called Unmagnetic Metals. 



We have as yet endeavoured to prove the magnetism of the 

 so called unmagnetic metals by attempting to direct or at- 

 tract them by strong magnets, or else by trying their power of 

 moving very light delicate magnetic needles; both methods 

 however without success. In the above experiments we have 

 demonstrated the hindering influence of the electrical currents 

 induced in iron during its magnetization, and this excited a 

 hope of being able to let the weak magnetism of these metals 

 appear, by preventing the formation of those electric cur- 

 rents. This was crowned with complete success ; for while 

 massive bars of antimony, bismuth, lead, tin, zinc, copper and 

 brass weakened the current a/3, so that when the equilibrium 

 was destroyed, a magnetic needle indicated the direction of the 

 current as being from /3 to «; on the contrary, the current 

 was strengthened, or the direction became from « to /3 when 

 those substances were introduced into the spiral a 6 in the 

 form of well-isolated wires. 



XXXIII. Reply to the Inqniry in the Supplement Number of the 

 Philosophical Magazitie Jo?- January 1842, respecting a 

 Manuscript at Oxford on the Rectification of the Circle. By 

 William Rutherford, I^sq.* 



¥N the Supplement Number of the Philosophical Magazine 

 ^ for January 184'2, Mr. Halliwell inquires whether I can 

 give him any information respecting a manuscript at Oxford, 

 said to contain the computation of the ratio of the diameter of 

 a circle to its circumference to 154 places of figures. 



I have not seen the manuscript to which I have alluded in 

 my paper on the Rectification of the Circle in the Philosophi- 

 cal Transactions ; but I have no doubt whatever that such a 

 manuscript does exist, and my belief is strengthened by the 

 fact that the figures in the ratio are there correctly computed 



* Coiiinuinicated by tlie Author. 



