48 PROFESSOR ©. G. KNOTT ON MAGNETIZATION 
Tapue D. 
1 2atonlas 57°] 93°:5 
- Field. 
Ie Il. ie Il. I. | Il. 
30 349 901 376 754 405 647 
22 215 613 233 543 260 ATT 
14 109 341 121 321 140 297 
When this discrepancy was noticed, the first idea was that some fundamental mis- 
take had been made in reducing one of the series of experiments. The mistake might 
have been made either in calculating the field in C.G.S. units or in calculating the 
changes of resistance.* It is important to make sure that no such mistake has been 
made. I shall therefore reproduce exactly the observed numbers in two distinct 
experiments, one made on 19th June 1902 with the first apparatus, the other made on 
13th February 1903 with the second apparatus. Anchor-ring coil I. had 846 turns, — 
with a mean radius of 3°6 em.; and anchor-ring II. had 344 turns, with a mean radius 
of 9:1 cm. Hence the reducing factors which enable us to calculate field from current 
are in the ratio of about 6°2 to 1. Now, in the two experiments mentioned above, 
the measured deflections of the currents on the Kelvin graded galvanometer were, 
respectively, 9°9 with the magnet at mark 44°35, and 22 with the magnet at mark 16; 
that is, the currents were in the ratio of 44°35 x 22 to 9:9 x16; that is, about 6°3 to 1. 
Hence in these two experiments the fields were nearly the same, somewhere in the 
neighbourhood of 26. The following are the readings as jotted down in the experi- 
mental note-book, with the deflections and differences immediately deduced from them. 
Experiment 1.—Field = 26°'5. 
(1) Calibration of galvanometer. 
Reading on Seale when Current is 3 
5 Se en C Difference of 
Shunt in A, Deflection. Dedeonons 
Direct. Reversed. Direct. 7 
inf. 134 173 134 +39 Sw 
20 166 Ae? 1657 = iF 64:8 
inf. Teyece 174 133°1 +40°8 Sor 
20 165 142 165 = 25) 64:3 
inf. Wayaty yates | 132°6 +41°8 ah 
mean = 64°55 
* The constancy of the resistances of the various coils in use and the steadiness of the results obtained in all cases. 
quite preclude the possibility of any error in the estimation of the constants arising from faulty insulation. 
