466 Notes and Memoranda. 



paper." These researches showed that for an equal solar elevation the relative 

 intensities of the two regions varied considerably, even when no distinct clouds 

 appeared, and this variation seemed connected with hygrometric phenomena 

 in the lower regions of the atmosphere. At Paris, Lyons, and in Switzerland, a 

 certain south wind augmented the transparency of the atmosphere, and then the 

 difference between the two regions of the sky at right angles to each other was 

 least considerable, while if a west wind began to blow the relation of the two 

 rapidly converged towards unity. An east wind after rain caused a maximum of 

 difference between the two sky regions, but the persistence of this wind brought 

 back a minimum difference. A sombre mist near Paris and Lyons considerably 

 diminished the reflecting power of the atmosphere near the horizon. On mountain 

 heights, when the zenith and horizon were more than 90' apart, the difference was 

 more striking than on plains. Prom all his observations M. Chacornac concludes 

 that " the margin of the disc of our planet " must appear to an observer situated 

 outside it in space, " like that of Saturn and Mars, brighter than the central 

 regions, and this indicates that the atmosphere of Jupiter differs from ours, and 

 from theirs, for it appears like the fogs which overhang great cities." 



Novel Use oe Polarized Light. — In concluding the paper from which the 

 preceding facts are taken, M. Chacornac states that, from the shores of Lake 

 Neuchatel he watched small cumulus clouds that formed themselves soon after 

 sunset, and found them appear as bright spots seen on a dark ground, or as dark 

 spots on a bright ground, according to whether he shut out the polarized rays, 

 or let them reach his eye. From this it appeared that the proportion of polarized 

 light was sufficiently great, that dark spots became luminous through the action of 

 the analysing prism, and thus, passing from the condition of negative to that of 

 positive vision,* could be seen further off. The region of maximum atmospheric 

 polarization he states to be near the horizon about 78° from the sun, it there 

 amounts to about J£ of the total light which the atmosphere reflects. He suggests 

 that by adding an analysing prism to the eye-piece of a telescope, distant capes at 

 sea, and other objects, might become visible, just as he was able by such 

 means to see alpine summits after they been completely screened from ordinary 

 vision by a light fog. 



Action of Aeomatic Plants on Silkwoems. — M. Ern. Faivre detailed to 

 the Prench Academy experiments made by placing silkworms on screens pierced 

 with holes and fitted into boxes above a layer of the leaves to be tried. The worms 

 exposed to the action of wormwood were much excited, and they tried to get away. 

 The pulsation of the dorsal vessel was augmented, and their bowels purged. In 

 a few hours death ensued. Fennel produced similar effects on the nervous system 

 and a more marked one on the secretions. Balsam-tansy acted still more power- 

 fully, even killing the sick worms, and causing the healthy ones to emit their silk. 

 Common tansy was less violent. The effects depend upon the quantity of the 

 odoriferous herbs employed, and on the condition of the silkworms. When 

 healthy worms were supplied with mulberry leaves and exposed to the aroma of 

 the vegetables mentioned, they eat their food and made cocoons which were con- 

 sidered of superior quality. 



* Negative vision is when a dark object is seen, not by its own light, but by contrast with the 

 light surrounding it. Positive vision is when an object is visible by the light which it emits or 

 reflects. 



