Letter from Alexander Muirhead, FRS, The Lodge, Shortlands, to James Mackenzie Davidson Informs Mackenzie Davidson that he has just taken a look at Shallenhager's patent. Notes that one cannot tell if it is valid without studying other publications which would be too large a job for him to undertake. Explains that since 1895 there has been a good deal done in the regulations of the current in inductance coils. Asks if Mackenzie Davidson has tried to increase the power factor of his induction coil by putting an adjustable inductance coil in the primary current. 17 December 1904