Hakt. — On Terrestrial Magnetism. 129 



gestions may be made to execute criminal acts, and the unfor- 

 tunates, powerless to resist even when their better judgment is 

 awake, may carry them out to their fullest extent. The possi- 

 bilities of this new agent appear unlimited, and so fraught 

 with danger to the welfare and happiness of mankind that the 

 aid of the Legislature in France and elsewhere is sought to 

 control and regulate its practice. And if this is true — if the 

 suggestions of one mind can sway another to all that is im- 

 moral or criminal, if our natural gifts can thus be held in 

 abeyance, and the machinery of our inner life be moved by the 

 animal energy or the ideas emanating from another mind — 

 what becomes of our personality— the Ego, as it is called — 

 and all its responsibilities ? Startled at the momentous ques- 

 tion and all that it implies^bewildered- — we mutter with the 

 musing Macbeth, — 



Can .such things be, 



And overcome us like a summer's cloud. 



Without our special w onder ? 



AiiT. XV. — On Terrestrial Magnetism. 

 Bv the Hon. Eobeet Hakt. 



[Read brforc the Wellington PJalosophical Society, 19th February, 1890.] 



Observations on the subject have determined that the mag- 

 netism of the earth is that of a hollow sphere. The problem 

 here proposed for solution is the constitution of that hollow 

 sphere. 



The earth, an oblate spheroidal mass, having a diameter at 

 the equator of about eight thousand miles, travelling through 

 space at the speed of about nineteen miles in a second of time, 

 is held in its place toward the sun by the centripetal and 

 centrifugal action of its gravity in motion. 



While so travelling and so kept in its place the earth 

 revolves upoii its axis in rather less than twenty-four hours, 

 carrying with it on its surface an elastic cushion, called its 

 atmosphere. This atmosphere consists of air containing 

 oxygen and hytlrogen gases interfused with a trace of a third. 

 Observations on the aberration of light have determined the 

 depth of this atmosphere from its outer surface to be between 

 forty-five and fifty miles. That to the depth of forty miles 

 from its outer surface this atmosphere is absolutely dry must 

 appear from the fact that water in a state of vapour would at 

 that distance from the surface of the earth lose the beat 

 needful to keeping it in that state. Even at his place of observa- 

 9 



