TRANSACTIONS OF THE SECTION'S, 31 



to height amounted to anything like that assigned by M. KupfFer, 

 it could not have failed to be at once sensible. As it was, until 

 those calculations were made he did not see sufficient evidence to 

 prove any decided diminution*. 



On the Direction of Isoclinal Magnetic Lines in Yorkshire. By Pro- 

 fessor Phillips. 

 Observing with reference to the course of the lines of equal dip on 

 the earth's surface that instances occurred, as for example between 

 Ireland and England, of the abrupt flexure or shifting of the lines, 

 for which no reason had been assigned, the author proposed to him- 

 self to determine in a part of the North of England the exact course 

 of the isoclinal lines across a country of verj"^ peculiar physical con- 

 formation, so as to learn how far flexures and breaks of these lines 

 depended on the relative height and mass of elevated land. The 

 direction of the principal masses of high ground in Yorkshire is very 

 favourable to such an inquiry, because the two great hilly regions of 

 the county are separated from each other by a wide, deep, level 

 vale ranging along the actual magnetic meridian; and thus by select- 

 ing points in two circles round the city of York as a centre, one 

 constant point of reference could easily be had, and the experiments 

 repeated as often as needed, in order to test completely the depend- 

 ence of the direction of the magnetic lines on the geological and 

 geographical configuration of the country. The researches, though 

 incomplete, had been carried so far as to give reason to believe that 

 across the two hilly regions and intermediate vale in question 

 the lines of equal dip were not straight, but bent to the south 

 in the vale, and turning up to the north on the hills. Hence 

 it would appear that the dip of the needle decreases as we rise 

 above the surface of the earth, so as to be well recognised at mode- 

 rate heights. The author proposes to complete his observations 

 on an extended scale, and to add the results of some other ex- 

 periments contemporaneously made as to the lines of equal (total) 

 magnetical intensity. 



On the Direction of the Isoclinal Lines in England. 



Professor Lloyd gave a brief account of a series of observations 

 on the direction and intensity of the terrestrial magnetic force, 

 which he had recently commenced in England. The stations of the 

 observations hitherto made extended from the North of Wales to the 



* Since this communication was made the calculations alluded to have been per- 

 formed, and from the agreement of different series made with different needles, 

 both in the Alps and Pyrenees, the author conceives that he has demonstrated the 

 existence of the supposed diminution and approximated to its amount, which is 

 .j^ig-jj. of the horizontal intensity for every 3000 feet of vertical ascent. 



