364 Mineral Waters of Canada. 



If now we take the line of equal magnetic action, as it has 

 been accurately defined, by its relations to the horizontal force in- 

 stead of the temperature, we have to consider the amount of the 

 variation of the horizontal force from the minimum at 10 a. m. to 

 the time of greatest hourly variation, at 1 p. m., and enquire how 

 far to the north of B we must go to oh tain a horizontal force as 

 much less than that at B as that at B is greater than that at A. 

 But we here meet with a difficulty, inasmuch as the horizontal 

 forces, so called, at B and C (to the north of B), to be compared, are 

 really only the portions of the entire horizontal force, which are 

 due to the action of the variable stratum. The difference be- 

 tween these forces is very much less than that which subsists be- 

 tween the actual horizontal directive forces acting upon the 

 needle, but how much less we have no means as yet of ascertain- 

 ing with any certainty. For this purpose we must know the 

 proportion which the force of the variable stratum bears to that 

 of the whole magnetic stratum. 



Conjectures might be made as to the probable value of the 

 proportion between these forces, but without attempting to enter 

 upon such uncertain ground, I will content myself with remark- 

 ing that no proportion which, in the light of the investigations 

 of this and the previous paper, seems probable, gives movements 

 of the line of equal surface magnetic force materially less than 

 those of the isothermal line, above determined. 



As to the question of the intensity of the disturbing force 

 which produces the diurnal variations of declination, it is, in the 

 first place to be observed, that that portion of the horizontal force, 

 which is due to the action of the variable stratum, is entirely 

 effective in displacing the needle in a direction toward the per- 

 pendicular to the line of equal magnetic action of this stratum. 

 Now it appears, upon calculation, that this force must be as much 

 as thirty times its daily variation, in the summer, to produce upon 

 the supposition of a displacement of this line to the amount of 



6°, a change of declination amounting to 12'. 





Art. XXVI. — Chemical Examination of the Water of the Tus- 

 carora Sour Spring 1 , and of some other Mineral Waters of 

 Western Canada ; by T. S. Hunt, Chemist and Mineralogist 

 to the Geological Commission of Canada. 



In the autumn of 1847, I visited in the discharge of my duties, 

 a portion of the province which lies to the west of Lake Onta- 

 rio, and while there, collected several mineral waters, some of 

 which have proved of unusual interest. The results of my ex- 

 aminations appear in our report presented to his excellency the 



Earl of Elsrin. Govp.rnnr-prpnprnl af flip. Province, on the 1st 01 



