Intelligence and Miscellaneous Articles. 397 



The "observed" values are the wave-lengths, as determined by Dr. 

 Wolcott Gibbs (Araer. Jour. Sei. \2'\ xliii. p. 4), ol: the correspond- 



inff lines on Kirchhoff's scale. It seems likely that - may be a 



' ^z ' 



bright line, and thus belong to the new tield of investigation which 



Dr. Draper has opened by his paper on the discovery of oxygen in 



the Sim. The doubtful line (?) is midway between Kirchholf's line 



2869-7=430-37, and H=397-16. 



As alternate planets in the solar system, so alternate Fraunhofer 

 lines appear to obey the simplest law, intermediate values being 

 governed by laws of mutual equilibrium. The figurate symmetry 

 of the denominators for those alternate lines {n-\-a, n + Sa, n + Ga, 

 ji + lOa) is specially noticeable, and suggestive of my equation be- 

 tween the principal planetary masses : — 



(Neptune)^ X (Uranus)^ x (Jupiter)^ x (Saturn)~^°= 1. 



Haverford College, 



August 23, 1877. 



ON THE FLUORESCENCE OF THE LIVING RETINA. 

 BY M. YON BEZOLD AND DR. G. ENGELHARDT. 



Studies on the laws of colour-mixture, some years since, sug- 

 gested to one of us the question whether the fluorescence observed 

 by Helmholtz*, and afterwards by Setschenow t, in the dead retina 

 could not also be demonstrated in the liAdng structure. Experi- 

 ments made at that time, however, gave no result, but rather led 

 to the conviction that the solution of this problem would be possible 

 only in conjunction with an ophthalmologist. 



Interest in this subject was awakened afresh by the path-opening 

 discoveries of Boll and Kiihne, since through them all inferences 

 from the dead to the living retina must appear in the highest degree 

 doubtful. This induced us to attack the investigation jointly, the 

 results of which are communicated in the following. 



Before all things it seemed requisite to observe ophthalmoscopi- 

 cally the retinal picture of a spectrum, and then to try if it could 

 be displaced so far behind the pupillar margin that at last we 

 should have before us the retina in ultra-violet illumination only. 

 To this end the fan of coloured rays issuing from the prism was 

 received by the speculum so near that the whole of it fell upon the 

 latter. Then, by a suitable choice of distances and of the lenses 

 employed (the observations were always made on the inverted 

 magnified picture), it was possible to produce on the retina so small 

 a picture of the spectrum that the whole of it, or at least the 

 greatest part, could be viewed simultaneously. 



The result was a very surprising one, and, although at the com- 

 mencement neither sun-light nor quartz prisms were employed, 

 already contained in itself the wished-for issue, which, it is true, 

 had then to be rendered perfectly capable of demonstration by 

 varying and perfecting the experiments. 



The retinal picture of a spectrum shows, namely, peculiarities 



* Poggeiidorft^'s Annalen, vol. xciv. p. 205. 

 t Arch.f. Ophth. vol. v. p. 205. 



