SCIENTIFIC SUMMARY. 
215 
Reflection and Refraction. — Within the last few years Professor J. Clerk- 
Maxwell has shown the possibility that all electrical phenomena are due to 
pressures in the same ether, and this has long been assumed as the means of 
the propagation of light. Acting upon this assumption, he has deduced 
what the laws of transmission of light in ordinary crystalline and mag- 
netised media would be, and from such deductions he arrived at the laws 
of these phenomena. In a paper recently read before the Royal Society, 
Mr. G. F. Fitzgerald, F.T.O.D., investigates the laws of the reflection and 
refraction of light upon the same assumption, and he has obtained the same 
results as Professor M’Cullagh long ago deduced from his theory, and which 
are known to represent almost exactly the laws of reflection and refraction 
at the surfaces of ordinary and crystalline media. Still further, he investi- 
gated the laws of reflection at the surfaces of magnets, with theoretical 
results which essentially agree with and completely confirm Mr. Kerr’s re- 
cently published experiments on the reflection of light from the pole of a 
magnet. 
The Magic Mirror of Japan forms the subject of a communication 
recently made to the Royal Society by Profs. Ayrton and Perry. 
Its distinguishing property is that of u apparently reflecting from its 
polished face the raised characters on its back.” 
The mirror is of bronze, convex, polished with a mercury amalgam,, 
and bearing at its back a raised design. 
Sir Charles Wheatstone, in 1873, appears to have noticed the instrument, 
supposing that the maker “ scratched a pattern on the surface, which, after 
being polished, showed no traces of the scratches when looked at directly 
but when used to reflect the sunlight on to a screen revealed the pattern as 
a bright image.” 
As early, however, as 1832, Mr. Prinsep had given an account of the- 
mirror in the “ Journal ” of the Asiatic Society of Bengal, concluding that u the 
thin parts are slightly convex with reference to the rest of the reflecting 
surface,” and thinks it probable that “ part of the metal was by stamping 
rendered in a degree harder than the rest, so that in polishing it was not 
worn away to the same extent.” 
Various explanations had been offered by Mr. Highley, Sir D. Brewster* 
and others. Even the Roman writer Aulus Gellius appears to have beeu 
acquainted with the instrument. 
The authors of the paper saw that the employment of beams of light of 
different degrees of convergence or divergence would furnish a test for de- 
ciding the cause of the whole action. Molecular differences of surface would 
be practically independent of these factors ; whereas if the effect were due 
to portions of the surface being less convex than the rest, a complete inver- 
sion of the phenomenon might be expected to take place under proper con- 
ditions. This was found to occur. 
The method of producing this distortion by means of an iron rod is- 
explained at length. 
Self-luminous Clock Dials. — Dr. Henry Morton, President of the Stevens 
Institute of Technology, publishes interesting details on this subject. He 
has made an analysis of the substance with which the dials are coated, and 
found it to consist of the well-known phosphorescent compound, sulphide of 
