TRANSACTIONS OF SECTION A. 561 



Another point of interest is the effect of the sea, which is not, as is generally 

 supposed, actually to decrease the amplitude of annual temperature oscillation, 

 but to increase it, although to a less extent than a corresponding surrounding area 

 of land. Thus at Nertchinski-Zavod, in Siberia, the effect (calculated as above) of 

 the secondary cause, i.e., the surrounding land, on annual temperature variation 

 has an amplitude of 55° F. ; whilst at Kow, in the same latitude, the effect of the 

 surrounding land and sea has only an amplitude of 8°-3 F. The figures for sea 

 temperature are inadequate for effective numerical analysis, but they suggest a 

 possibility of arriving on these lines at a definite comparison of inland and marine 

 climates. 



5. A Neio Point of View about Gravitation, and a proposed Experiment. 



By Dr. V. Cb^mietj. 



We know perfectly well the quantitative law of gravitation, but we have na 

 idea of the mechanism of the attraction. 



Several attempts have been made to explain gravitation by the presence of a 

 medium, but, I believe, all without success. Some learned men, too, had the 

 idea of finding by experiment whether the propagation of attraction Avas in- 

 sttantaneous or not ; but, as far as I know, no physical experiment was ever tried. 



Whenever a system is in equilibrium ever}' attempt to disturb that equi- 

 librium will introduce new forces into the system, which will act against this 

 disturbance of equilibrium. 



There are many examples: heating of gases by compression, increase of 

 resistance of metals with temperature, and consequently, when they are sub- 

 mitted to an electromotive force ; and, moreover, the law of Lenz in induction. 



T thought that gravitation must very likely follow that universal law. 



If, for instance, we consider the two bodies A. and B in equilibrium, we can 

 imagine that there is a ' flux of attraction ' between them. Let us move A very 

 quickly : this motion will produce a sudden variation in that flux, and a reaction 

 will take place in the system at that moment which will work against the motion 

 communicated to A. 



A few months ago I described in the ' Comptes Rendus ' a new very sensitive 

 kind of balance which gives us an easy and direct way of verifying that idea. 



This balance is made in the following manner : a very light tube of aluminium 

 is horizontally suspended by a silk thread, the two bent parts of which form an 

 angle of about 120°. 



At one end of this tube is fixed a small sphere of platinum weighing about 

 three grammes. At the other end is a permanent magnet suspended by a silk 

 thread ; the weight of this magnet is three or four milligrammes lighter than that 

 of the sphere. 



A coil is fixed on the support of the apparatus, and the silk thread bearing 

 the permanent magnet coincides with the axis of that coil. 



On sending a current through it in the proper direction a repulsion between 

 the fixed coil and the permanent magnet will be established. That is the repulsion 

 which will be used instead of weights. 



I have constructed several of these balances for use as galvanometers or 

 electrometers. The measured accuracy of one was as follows : 



It gives, at a distance of two metres, a deviation of 12 millimetres for a 

 current of 10~' amperes, which corresponds on the movable magnet to a force 

 of 3 X 10"'' dynes. This is the maximum obtained as yet. But I can easilv 

 obtain the 10~* of a dyne ; and I hope, with the long arm constructed foV 

 my gravitation experiment, to each about the 10~" of a dyne. 



Now, with a convenient current, let us produce equilibrium between the 

 magnet and the sphere. We will record it by the position of a spot of li^ht 

 reflected by a mirror. If, then, we bring near to the sphere a heavy sphere 

 of lead, there will be an attraction between them ; we can equilibrate it by 

 increasing conveniently the current in the soil. 



