782 POPULAR SCIENCE MONTHLY. 



Cavendish experiment, in which the attraction of lead balls of 

 known mass is measured by means of a torsion balance, and so 

 compared with the attraction of the earth ; and the Schiehallion 

 experiment, in which a plumb line is suspended near a mountain of 

 known mass, and the deflection of the line from the vertical care- 

 fully measured. But both experiments proceed upon the assump- 

 tion that all matter attracts, and prove nothing. 



This review of the Newtonian conception serves as a preface 

 to the authors' own theory, which is a direct outgrowth from the 

 four primary principles deduced in an earlier book persistence, 

 resistance, reciprocity, and equalization. Briefly stated, their 

 theory is that two bodies in different states of excitation and free 

 to move will move toward each other, the intensity of attraction 

 being proportional to the difference in the excitation. Bodies in 

 the same state that is, in equilibrium have no attraction for 

 one another, and there will be no gravitation manifested between 

 them. This is a direct contradiction of the Newtonian position 

 that gravitation is universal. The excitation of a body may be 

 increased by heat, light, electricity, or magnetism, and conse- 

 quently the attraction, weight, or mass may be changed by a 

 change in the physical conditions. This has been repeatedly 

 shown by experiment, but with the idea of the unchangeableness 

 of gravity firmly fixed in the mind the results of the experiments 

 have always been explained on other grounds. According to the 

 new view, terrestrial gravitation is entirely due to the different 

 states of excitation which prevail on the outside of the globe and 

 on the inside, and notably to the difference in thermal condition. 

 Heating a body on the surface of the earth ought, by lessening 

 this difference, to reduce the attraction that is to say, the weight 

 and such is actually the case. Every one who has worked in the 

 laboratory knows that a hot platinum crucible weighs several 

 milligrammes less than the same crucible when cold. This was 

 formerly attributed to ascending currents of hot air, but the ex- 

 planation no longer holds. These and other similar experiments 

 have recently been repeated under conditions which do not admit 

 the existence of convection currents, and the loss of weight is 

 still observable. 



With permission we quote from a letter recently received from 

 Mr. Paul R. Heyl, of Philadelphia : " I have been making a curi- 

 ous experiment since I got back within reach of an analytical 

 balance. I took a piece of three-quarter-inch glass tubing, sealed 

 it at one end, and choked it slightly about one inch from the sealed 

 end. In the lower chamber thus formed I placed dilute sulphuric 

 acid, and dropped in a piece of solid caustic potash, which was 

 arrested at the choke. I then sealed off the upper end of the tube 

 about two inches above the choke. This arrangement I then 



