264 



SCIENCE. 



[N. S. Vol. IX. No. 216. 



tliird class is the complex dream which may be 

 determined by difTerent kinds of stimuli succes- 

 sively applied. These reports also suggest a 

 practical matter that those who find dream 

 pleasures a necessity, as the opium eater, might 

 obtain a large measure of such pleasures by per- 

 fume and other stimuli which do not leave un- 

 healthy reactions. 



As to my own dreams I may mention a few 

 facts which may be suggestive. My dreaming 

 is commonly of places and persons which are 

 totally unknown, but, of course, the types are fa- 

 miliar. I often dream of being in a crowd and 

 studying faces which I have never seen before. 

 Similarly I dream of being in a bookstore and 

 picking up new books which I have never seen, 

 and reading many pages, and looking at strange 

 pictures. I once awoke from a vivid dream of 

 this sort, and was able to recall several sen- 

 tences, and to notice that they were far from 

 my own style of writing, and had an individu- 

 ality of their own which I could not recognize. 

 But all this merely means that those in whom 

 the constructive imagination is strong exercise 

 it freely in sleep. 



A singular case of dream stimulation is this : 

 I dreamed of being in a strange hilly country, 

 and a man appeared driving a tandem. In 

 vain he sought to get up the hills, and the horses 

 became so ludicrously tangled that I burst into 

 loud -laughter ; this was heard in another room. 

 In my laughter I heard other voices laughing, 

 all from a single direction, but there was no 

 visual image. It is highly probable that my 

 dream of hearing others' laughter was stimu- 

 lated by hearing my own laughter. 



Maury makes the ' embryogeny of the dream' 

 to consist in 'hypnagogic hallucination,' that is, 

 in the stage of waking just previous to sleep 

 visual and auditory hallucinations occur which 

 are carried into sleep, but it appears to me that 

 he lays much too great stress on the point. I 

 noticed the other morning during a succession 

 of cat-naps that the formation was not in any 

 wise hallucinatory. Awake for a few seconds 

 I thought of dressing, and had the images of 

 the process but not hallucinatory, but knowing 

 them to be ideas to be realized, but the senses 

 quickly falling asleep, these images constituted 

 a dream reality, I was really dressing. Very 



commonly our last waking thoughts turn into 

 dream without any hallucinatory stage. 



Hiram M. Stanley. 

 Lake Forest, III., January 23, 1899. 



TROWBRIDGE'S THEORY OF THE EARTH'S MAG- 

 NETISM. 



In an article entitled ' The Upper Regions of 

 the Air,' in the January number of the Forum, 

 Professor John Trowbridge proposes a new 

 theory to account for the phenomena of the 

 earth's magnetism, of the northern lights and 

 of thunder storms. 



His theory, briefly stated, is that those waves 

 of energy coming from the sun whose wave- 

 lengths are of the order of those concerned in 

 the X-ray phenomena are completely absorbed 

 by the atmosphere and transformed into elec- 

 tric and magnetic energy in the upper regions 

 of the air, and that being thus transformed they 

 fail to manifest themselves as light at lower 

 altitudes. According to Perrin and Winkel- 

 mann, the X-rays have the property of commu- 

 nicating an electric charge to conductors. " If, 

 therefore, X-rays reach the earth from the sun 

 they are competent to give an electrical charge 

 to our atmosphere. The side, therefore, of the 

 earth turned toward the sun would receive a 

 charge in the upper good-conducting regions of 

 the air. This cliarge would tend to dissipation, 

 and there would be a flow of electricity toward 

 the side of the earth not turned to the sun. 

 The rotation of the earth on its axis from west 

 to east would bring forward at each revolution 

 fresh regions of the upper air to receive the 

 electrical charging from the sun. There would 

 be an accumulation of electricity on one side of 

 the earth and a diminution of electricity on the 

 other. The conditions of the equalization of 

 the electrical charge, or the flow of electricity, 

 might be determined by the direction of rotation 

 of the earth. If this flow took place from east to 

 west, just opposite to the direction of rotation 

 of the earth, and were sufficiently powerful, it 

 would produce the magnetic north and south 

 poles. It has been found that air submitted to 

 the action of the X-rays continues for some 

 time to manifest their influence. We should, 

 therefore, expect a fall of electric pressure be- 

 tween the regions just entering into daylight 



