Chase. J 358 [November. 



tation of the manner of mining coal, showing the various 

 operations in detail with the late improvements introduced. 



Mr. P. E. Chase made a communication on the specific 

 magnetism of iron. 



In my communication on the numerical relations of gravity and 

 magnetism (Trans. A. P. S., vol. xiii, p. 126), after adducing var- 

 ious evidences of a correlation that had been long suspected, I en- 

 deavored to obtain approximate valuations for the constant factor, K, 

 which was introduced in the comparison of the tidal forces with the 

 force of equilibrium. These approximations led me to "suggest the 

 propriety of considering the element of density (or of its correlative, 

 the square of the time of molecular diffusion), in connection with 

 both A and M." 



In the year after this suggestion was made. Dr. Menzzer announced, 

 as an experimental result (Poggendorff's Annalen, Nov. 1865; P. 

 Mag., XXX, 456), that "the magnetizing powers of two coils which 

 give the maximum of intensity are as the square roots of their 

 weights." It therefore appears, 



1. From Grraham's and other well-known laws: 



Elasticity cc specific heat oc (wave-velocity).^ 

 Density oc (time of molecular diffusion).^ 

 Weight oc (time of sonorous vibration).*^ 



2. From observations on terrestrial magnetism : 



Tidal differences oc (magnetic differences).'' 

 Magnetic variation oc (time).''^ 



3. From Menzzer's experiments: 



Weight oc (magnetizing power). ^ 



This indirect confirmation, of a conjecture which was at first based 

 on a plausible analogy, encourages me to hope that the following 

 comparisons between molecular and cosmical kinetic values may help 

 to explain the specific magnetism of iron. 



According to Tredgold, iron may be elongated about y^'fjo without 

 permanent alteration of structure. Now the ratio, at the earth's sur- 

 face, of solar to terrestrial attraction, is about jq\q, and four times 

 the ratio of the specific gravity of air to that of iron varies, approx- 

 imately, between y^'o^ and yT^gg- Although this range of variation 

 is somewhat more than ^ of the least value, or about g^gg of the 

 total force, it is but little greater than Helmholtz found in the vibra- 

 tion-ratios for the first overtone of a series of tuning-forks (5.8 to 6.6 

 times the fundamental), while it is much less than the daily flue- 



