214 Scientific Intelligence. 



variable. If the instrumental corrections for the two electro-mag- 

 nets are equal, this orbit will be the first of the series for the 

 unison ; that is, an oblique straight line. If this is not the case, 

 it will be convenient to make it so, by introducing resistances at 

 the proper place in the circuit. Then, the apparatus is ready to 

 be put to the work of measuring the velocity of electricity. An 

 additional length of resistance coil is introduced, sufficient to 

 change the orbit to some other in the series. The best one to 

 select is the straight line which inclines in the opposite direction. 

 The new orbit proves that one of the forks begins a vibration by 

 half a period behind the other fork ; which, in this particular case, 

 is 2-^ of one second. This fraction of a second is the transmis- 

 sion time for the passage of the current through the additional 

 resistance coil. Unison forks of higher pitch would register 

 smaller fractions of time. So would also forks, in which the ratios 

 of vibration were less simple ; but the orbits would be more com- 

 plex and could not be observed with the same precision as the 



I have perfected the apparatus, just described, to such an ex- 

 tent as to feel assured of its adaptation to the purpose which has 

 been specified. But I wish to make a larger number of observa- 

 tions, upon different lengths of resistance and under various com- 

 binations, before I give numerical results. 1 propose, hei'eafter, 

 to subject in this way to experimental trial, the theoretical law 

 that the transmission time increases with the square of the dis- 

 tance, and that the velocity is inversely as the distance. If this 

 law holds good, the unit time and the unit velocity may be found 

 for a unit distance, or a unit resistance, and then the time and the 

 velocity can be computed for any other distance or resistance. 

 This unit time and unit resistance' must be accurately calculated 

 from a combination of all the results of the various experiments. 

 It is also desirable to ascertain the time and velocity for coiled 

 and uncoiled, for naked and covered conductors ; as also for air 

 lines and ocean lines. It is to be observed that, in all cases, the 

 time and velocity ascribed to the passages of the electricity apply 

 to that amount of electricity which is required to work the receiv- 

 ing instrument. 



SCIENTIFIC INTELLIGENCE. 

 I. Chemistry ajj^d Physics. 

 1. ProbUma in Chemical Dynamics. — In continuing his valua- 

 ble researches in thermo-chemistry, Berthelot has developed 

 some important facts in chemical dynamics. He finds that 

 sodium butyrate when crystallized contains three molecules of 

 water, all of which it loses in a dry vacuum or when heated to 

 110° C. The last half molecule of water is very persistent; so 

 that by careful management, a definite hydrate of this composition 



