Systematic Classification of the various Forms of Energy. 277 



N, the axis of the central lenses rnay be made to coincide 

 with the axis of the instrument ; the plane of the optic axes 

 is then parallel to the vertical fixed circle, the crystal being- 

 turned by this motion about an axis bisecting the obtuse angle 

 between the optic axes. 



IV. By turning the graduated circle with the arc T and the 

 arm I attached to it on the face of the fixed vertical circle (i. e. 

 round a horizontal axis perpendicular to the plane of the optic 

 axes), and reading the verniers on both sides of the circle, the 

 angles between the directions of the optic axes may be accu- 

 rately measured. 



XXXIII. An Attempt at a Systematic Classification of the 

 various Forms of Energy. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 



W"HILE writing a little elementary manual of mechanics 

 lately for Messrs. Chambers, my attention was di- 

 rected to a certain amount of vagueness and loose language 

 which appears to be current in modern statements concerning 



I venture, therefore, to ask you to publish in your Journal 

 the following remarks on the subject, the greater part of which 

 aim at embodying in a concise form what I understand to be 

 the doctrines of the mathematical physicists (though they do 

 not seem as yet to have been all clearly apprehended by phy- 

 sicists in general), while the remaining portion contains a few 

 points of view which have not, as far as I am aware, been 

 published ; and though doubtless they have occurred to others 

 besides myself, it would seem to be conducive to clearness of 

 thought and accuracy of expression to have them briefly set 

 forth in order, so that those which are erroneous or vague can 

 be the better detected, and those which are true and definite 

 can be the better apprehended. There can, I think, be little 

 doubt that it may ultimately be possible, and that it is exceed- 

 ingly desirable, to have all the fundamental doctrines of phy- 

 sic- stated in ordinary language without technicalities : but 

 unless such statements are accurate and devoid of vagueness, 

 they can be of little or no use. 



It will, I hope, be understood that the following attempts 

 at statements are in a dogmatic form simply in order to be con- 

 cise. Some improvement in the present language of text- 

 books is distinctly desirable ; and 1 hope that this communi- 

 cation may be suffieientlv suggestive to lead to a discussion, 



Phil. Mag. S. 5. Vol. 8. No. 49. Oct. 1879. U 



