56 BRITISH ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE. 



found at Point Barrow as elsewhere, •wherever similar inTestigations had beec 

 made, that in regard to the frequency of their occurrence, and the average amounts 

 of easterly and -westerly deflections, the disturbances folio-wed systematic la-ws 

 depending on the hours of solar time. The laws of the easterly and westerly were 

 also found at Point Barrow, or elsewhere, to be distinct and dissimilar. The 

 author explained how these observations, which manifestly related to those arising 

 from what were called " storm," were separated from the rest ; and when that 

 separation was effected, the law of the true solar variation w.as shown distinctly 

 to be observed. But upon instituting a comparison between the disturbance laws 

 at Point Barrow and Toronto, it was found that the laws of the deflections of the 

 same name at the two stations did not corresiDond ; but, on the other hand, there 

 existed a very striking and remarkable correspondence between the law observed 

 by the easterly at Point Barrow and the westerly at Toronto, and between 

 the law of the westerly at Point Barrow and easterly at Toronto ; and this- 

 correspondence was shown to exist not in slight or occasional particulars 

 only, but throughout all the hours in well-marked characteristics of both 

 classes of phenomena ; and it follows from the correspondence in the hours 

 at which opposite disturbance deflections prevail, that the portion of the 

 diurnal variation which depends upon the disturbances has opposite, or nearly op- 

 posite, characteristics at the two stations. The importance of eliminating these 

 disturbances from the regular march of the solar variation was then pointed out in 

 both: for when the diurnal variation is derived from the whole body of observa- 

 tions at Point Barrow, retaining the disturbances, the westerly extreme of the 

 diurnal excursion, which, as is well known, occurs generally in the extra-tropical 

 part of the northern hemisphere a little after 1 p.m., is found to take place at 11 

 P.M. ; but when these larger disturbances are omitted, the westerly extreme falls at 

 the same time as elsewhere — viz., 1 p.m.; and the author suggested the probability 

 that the anomalies which have sometimes been supposed to exist in the turning 

 hours of the solar diurnal variation in high latitudes may be susceptible of a similar 

 explanation. It appears, then, by a compai-ison of the Point Barrow and Toronto 

 observations, that in the regular solar diurnal variation the progression at the two 

 stations is similar, the easterly and westerly extremes being each reached nearly at 

 the same hours, whilst in the disturbance diurnal variation this progression is re- 

 versed. Another distinction exists in their magnitudes, which is found in the solar 

 diurnal variation to be as nearly as may be in the inverse ratio of the values of the 

 horizontal force at the two stations, (which is the antagonistic force opposing all 

 magnetic variation,) whilst on the other hand the increase in the range of the dis- 

 turbance variation is many times greater than it would be according to the same 

 proportion. It would appear, therefore, that the absolute disturbing force must 

 be much greater at Point Barrow than at Toronto. The author then proceeded to 

 point out the concomitant occurrences of the auroral manifestations. The observers 

 noted at each hour whether or not there was an auroral display: from 11 a.m, to 

 3 P.M. no auroral displays were ever observed ; but the number of them was found 

 progressively to increase from 3 p.m. to 1 a.m., and then again in regular progression 

 to decrease to 0, at 11 a.m. The frequency of the oecui-rence of the aurora may 

 be judged of, when it is said that during six months, — December, January and 

 February of 1852-5S, and the same of 1853-54, — the aurora was seen six days 

 out of every seven, The hour of the day at which no auroral display is ever ob- 

 served corresponds with the minimum of westerly disturbance, while the maximum 



