426 Scientific Intelligence. 



Reference is made to the question of earth currents. A com- 

 parison for thirty-one clays, between 1880 and 1891, of cases of 

 sudden magnetic movement and earth current, shows the earth 

 current to precede the magnetic movement by 0*14 minute, equiva- 

 lent to 8 seconds. The question of the relation between magnetic 

 movements and earth currents is discussed. The desirability of 

 being able temporarily to obtain, when occasion requires, a more 

 extended time scale for all magnetical and meteorological phe- 

 nomena is pointed out. 



The general result is that in the definite magnetic movements 

 preceding disturbance the magnets at any one place are simulta- 

 neously affected ; also that in places widely different in geographi- 

 cal position the times are simultaneous, or nearly so, a small con- 

 stant difference existing at some places which may be real or may 

 be accidental, but the character of which it seems desirable to 

 determine. It is shown also that at Greenwich definite magnetic 

 movements are accompanied by earth current movements which 

 are simultaneous, but that neither magnetic irregularities nor 

 ordinary magnetic variations seem to admit of explanation on the 

 supposition of being produced by the direct action of earth cur- 

 rents. — Proc. Roy. Soc, ~No. 313, p. 445. 



1 2. Physics, advanced course, by George F. Barker, Pro- 

 fessor of Physics in the University of Pennsylvania. 902 pp. 8vo. 

 New York, 1892 (Henry Holt and Company.) — The subject of 

 Physics has grown to so large proportions of recent years that to 

 present it adequately, in systematic shape and with such thorough- 

 ness as the higher grade of students demands, is a work of ever 

 increasing difficulty. To the accomplishment of this task Pro- 

 fessor Barker has brought a thorough grasp of the subject as a 

 whole, a comprehensive and minute acquaintance with the writ- 

 ings, both practical and theoretical, of the foremost workers and 

 thinkers in the science, and an unusual degree of skill and 

 experience in the clear presentation of facts and principles for 

 the benefit of students. The results of his labors, the careful and 

 patient nature of which are obvious from beginning to end, is a 

 work modern in method and fresh in matter, not indeed beyond 

 criticism at some points, but which commends itself to the atten- 

 tion of every teacher who has to do with this department. 



Physics in general is treated as " the science of energy " and 

 the three fundamental divisions adopted for the subject are those 

 of (1) mass-physics, (2) molecular physics and (3) physics of the 

 ether. In the first division the subjects discussed are kinematics, 

 dynamics, work and energy, attraction and potential, also the 

 properties of matter and finally the energy of mass-vibration or 

 sound. The second part includes heat ; while the third gives the 

 discussion of radiation in general : of electrostatics, called the 

 energy of ether-stress ; magnetism, " the energy of ether vortices " ; 

 electrokinetics, " the energy of ether flow". The last chapter treats 

 of the electromagnetic character of radiation. 



