October 31, 1890.] 



SCIENCE. 



247 



I give four of Professor Shuster's conclusions. 



" 1. The principal part of the diurnal variation [of the needle] 

 is due to causes outside the earth's surface, and probably to 

 electric currents in our atmosphere. 



" 3. As regards the currents induced by the diurnal variation, 

 the earth does not behave as a uniformly conducting sphere, but 

 the upper layers must conduct less than the inner layers. 



"4. The horizontal movements in the atmosphere which must 

 accompany a tidal action of the sun or moon, or any periodic 

 variation of the barometer such as is actually observed, would 

 produce electric currents in the atmosphere, having magnetic 

 effects similar in character to the observed variation. 



" 5. If the variation is actually produced by the suggested cause, 

 the atmosphere must be in that sensitive state in which, according 

 to the author's experiments, there is no lower limit to the electro- 

 motive force producing a curi'ent." 



Meteorologists are now becoming somewhat accustomed to see- 

 ing suggestions from generally recognized authorities, showing 

 the possibility of some kind of electric action taking place in the 

 atmosphere, though I do not claim that this view is accepted as 

 yet in any except an extremely limited sense as an explanation of 

 atmospheric phenomena. I do not fully understand sonie of Pro- 

 fessor Shuster's views. The expression " convection currents 

 which flovv" does not convey a definite meaning. Just how elec- 

 ti'ic currents are to be induced in the upper air strata by a wave 

 of heat is also not entirely plain. The expression "the horizontal 

 motion which must accompany the change in pressure,'' as applied 

 to the diurnal range of pressure, I think, simply means the hori- 

 zontal propagation of a wave of pressure, and not any actual 

 motion of air. I can hardly see how the convection currents of a 

 thermal wave with the minimum point in the lower air strata at 

 sunrise, and the maximum point about 3 p.m., can possibly induce 

 electric currents having critical points at 10.30 A.M. and 3 P.M. It 

 is generally accepted that the diurnal range of temperature in the 

 free air is practically nothing at heigbls above five thousand feet; 

 so that the supposed convection currents from the direct thermal 

 effect cannot induce electric currents in the upper strata. 



It seems to me there is also an objection to Dr. Hann's view, 

 that the diurnal range of air-pressure can be due to the direct 

 heat-action (Wdrmewirkung) of the sun upon the upper limits of 

 the atmosphere. 



I have very recently discovered a method of studying the diurnal 

 range of air-pressure and allied phenomena which seems capable 

 of great extension, and possibly of displaying many important 

 facts. For many years I have searched for a simple method of 

 separating out the accidental variations of pressure, temperature, 

 moisture, etc., in our atmosphere, produced by the progress of 

 high and low areas, from those which are more or les-s constant 

 in their action. It is quite well established that these highs and 

 lows (called by many "anticyclones" and "cyclones") have a 

 common progi-ession from west to east, especially in this country. 

 The plan proposed is to carry back the conditions observed at any 

 moment in the atmosp'oere to a point of time several hours before, 

 say twelve hours, or especially twenty-four hours. This becomes 

 a simple matter when we have a regular advance in a high or 

 low; for we can place its centre at the point where it was twelve 

 or twenty-four hours previously, and then at once read off the 

 amount of change at each station for either of those intervals of 

 time. During the month of August, 1890, I had occasion to try 

 this method for determining the diurnal range of air-pres'sure from 

 8 A.M. to 8 P.M., and vice versa ; and the results were of the high- 

 est interest. For example: on Aug. 6, at 8 P.M.. there was a fall 

 in pressure in twelve hours of from one tenth to two-tenths of an 

 inch from the Atlantic to the 107th meridian. The next morning 

 there was almost a complete recovery over this region. On the 

 8th in the morning there was a rise of from one-tenth to two- 

 tenths of an inch over the whole, and at 8 p.m. of the same day 

 there was a fall of one tenth of an inch over half, the above region. 

 I found the general tendency for this diurnal range in air-pressure 

 to be the same for both highs and lows, though the fall is gen- 

 erally slightly greater in the low, and vice versa in the high. It 

 should be noted that this diurnal range was often oblitei-ated, or 

 even carried in an opposite direction, in some parts of the country 



when it was impossible to centre exactly the two maps. There 

 was a law, however, showing a marked general rise in pressure in 

 the forenoon, and a corresponding fall in the afternoon. This 

 may be seen to be all the more remarkable, since the observations 

 were made at 8 a.m. and 8 p.m , 75th meridian time, and not at 

 10.30 A.M. and 3 p.m., which are the maximum and minimum: 

 points in the diurnal range. We see that these changes in air- 

 pressure are not due to the advance of any air- wave or of air-par- 

 ticles, for this would imply a velocity of over two hundred miles 

 an hour for this region alone. The rise in pressure in the fore- 

 noon cannot be due to an inflow of air from surrounding regions, 

 because the rise occurs over all the surrounding region. It seems 

 impossible to consider that any direct thermal effect can do more 

 than simply heat the air without changing its pressure. It seems 

 to me we are driven to the hypothesis that these changes are 

 brought about by some agency outside of the earth. Is it incredi- 

 ble to suppose that there is a thermo-electric action from the sun 

 upon the atmosphere propagated like a wave one thousand miles 

 l^er hour, which is the principal cause of the diurnal range of both 

 the magnetic needle and of air-pressure, and upon which other 

 effects may be superposed? H. A. Hazen. 



Washington, Oct. 18. 



Origin of Right or Left Handedness. 



The question of the nature and origin of right or left handed- 

 ness has given rise to much discussion in late years, the convic- 

 tion growing among investigators that it is due to some hidden 

 difference in the structure or function of the two hemispheres of 

 the brain. The best resume and general discussion of the question 

 is the learned monograph by Sir Daniel Wilson entitled "The 

 Right Hand and Left-handedness," being a reprint from the 

 " Transactions of the Royal Society of Canada," Section II,, 1886. 



In order to examine more particularly into the time at which 

 the child begins to show signs of marked preference for either 

 hand, I instituted a series of experiments upon my own child, 

 extending them over the greater part of the first year. As I have 

 no time at present to write up the results systematically, I wish 

 simply to announce a point or two which may be of interest to 

 students of the subject. 



1. I found no trace of preference for either hand as long as 

 there were no violent muscular exertions made (based on 3,187 

 systematic experiments in cases of free movement of hands near 

 the body: i.e., right hand 585 cases, left hand 568 cases, a differ- 

 ence of 17 cases; both hands 1,034 cases; the difference of 17 

 cases being too slight to have meaning). 



2. Under the same conditions the tendency to use both hands 

 together was about double the tendency to use either (seen from 

 the number of cases of the use of both hands in the statistics given 

 above), the period covered being from the child's sixth to her 

 tenth month inclusive. 



3. A distinct preference for the right hand in violent efforts in 

 reaching became noticeable in the seventh and eighth months. Ex- 

 periments during tlie eiglitli month on this cue gave, in 80 cases,, 

 right hand 74 cases, left hand 5 cases, both hands 1 case. In 



'many cases the left hand followed flovvly upon the lead of the 

 right. Under the stimulus of bright colors, from 86 cases, 84 

 were right-hand ca.ses, and i left-hand. Right-handedness had 

 accordingly developed under pressure of muscular effort. 



4. Up to this time the child had not learned to stand or to creepr 

 hence the development of one hand more than the other is not 

 due to differences in weight between the two longitudinal halves 

 of the body. As she had not learned to speak or to utter articu- 

 late sounds with much distinctness, we may say also that right or 

 left handedness may develop while the motor speech centre is not 

 yet functioning. 



Other points resulting incidentally are of interest in general 

 psychology: i.e., — 



5. At the end of the seventh month the child's visual estimation 

 of distance was exact enough to lead her invariably to refuse to- 

 reach for an object more than fourteen inches distant, her reach- 

 ing distance being from nine to ten inches (based on tabulated 

 experiments). Moderate stimuli she refused beyond thirteen 

 inches. 



