134 Mr. A. W. Ward on the Use of the Biguartz in 



Volts in primary, 128 Current in primary, 14*2 



„ secondary A, 119 „ secondary A, 8" CH *, 



„ secondary B, 119*5 „ secondary B, 8*2 J 



Connecting up the secondaries of transformers A and B in 

 parallel, the volts at the terminals of the primary being the 

 same as before, and the secondary circuit being lamps. 



Volts in primary, 128 I Current in primary, 17*4 

 „ secondary, 121 „ secondary, 16*3 



Here we have to give 17*4 amperes to the primary instead of 

 14*2 to get same current in secondary, and the volts in 

 secondary are practically the same as before. 



If we were being supplied with electricity, what should the 

 meter measure ? Surely the amount of energy we use. But 

 ordinary meters only measure ampere-hours, and so cannot 

 but give records in favour of consumer or supplier. The 

 sooner the public understand this, the sooner we shall have a 

 scientific meter in our houses. 



XX. On the Use of the Biquartz in determining the position 

 of the Plane of Polarization. By A. W. Ward*. 



THE biquartz has been so often used, especially on the 

 ■ Continent, by investigators on the rotation of the plane 

 of polarization of light, and with such extremely varying 

 degrees of accuracy, that it seems of interest to account for 

 these results mathematically. Verdet and H. Becquerel ob- 

 tained results which varied by less than 4'; while Wertheim, 

 Matteucci, Edlund, Liidtge, and Villari obtained results vary- 

 ing by as much as 2°. Liidtge has in one case obtained a 

 rotation of 4 C where, on his own showing, the light was circu- 

 larly polarized. Verdet's and Becquerel's accurate results 

 were obtained when rotation was looked for in liquids and 

 isotropic substances ; and the inaccurate results of Wertheim 

 &c. were obtained when seeking for a rotation in doubly- 

 refracting substances. In the former case the light remained 

 plane-polarized, in the latter it became elliptically-polarized, 

 and the position of the plane of polarization was really that of 

 one of the axes of the ellipse. In the present investigation 

 we shall then determine with what degree of accuracy the 

 biquartz can be used to determine the position of the axes in 

 elliptically-polarized light. 



Let us suppose that the elements of the elliptically-polarized 



* Communicated by the Physical Society : read June 8, 1889. 



