66 HENRY A. EOWLAND 



question of what is a molecule. To accomplish this we must obtain a 

 series of curves for the same ring between as wide limits of temperature 

 as possible. We must then plot our results in a suitable manner; and 

 from the curves thus formed we can find what would probably happen 

 if the temperature were lowered to the absolute zero, or were increased 

 to the point at which nickel is said to lose its magnetism. In such 

 inquiries as these the graphical method is almost invaluable, and little 

 can be expected without its aid. 



In applying the formula to this curve, we do not find so good an 

 agreement as at the lower temperature. I do not consider this conclu- 

 sive that the formula will not agree with observation at this tempera- 

 ture; for I have noticed that the curves of different specimens of iron 

 and nickel seem to vary within a minute range, not only in their 

 elements but also in their form. This might perhaps be accounted for 

 by some small want of homogeneity, as in the case of burning in iron 

 and nickel; but at present the fact remains without an explanation. 

 But the amount of the deviation is in all cases very small when all the 

 precautions are taken to insure good results. The nature of the devia- 

 tion is in this case as follows: when the constants in the formula are 

 chosen to agree with the observed curve at the vertex and at the two 

 ends, then the observed curve falls slightly below the curve of the 

 formula at nearly all other points. In a curve plotted about 5 inches 

 high and broad, the greatest distance between the two curves is only 

 about -^ of an inch, and could be much reduced by changing the con- 

 stants. For the benefit of those who wish to study this deviation, I 

 have calculated the following values, which will give the curve touching 

 the vertex and the two ends of the observed curve of Table III. They 

 are to be used by plotting in connection with that Table. 



3 + 25/C + 140 



I have not as yet obtained a complete curve of iron at a high temper- 

 ature; but as far as I have tried, it does not seem to be affected much, 

 at least for high magnetizing-powers. I have, however, found that the 

 maximum of magnetization of iron decreases about 2 per cent by a 



