56 PROCEEDINGS OF THE 



moon's crust. He might be justified by Piof. Seechi's drawing of Copernicus, in 

 inquiring if the low excurrent buttresses may indicate issues of lava on the south- 

 ern and western sides ? On the whole, the author is confirmed in the opinion he 

 has elsewhere expressed, that on the moon's face are features more strongly marked 

 than on our own globe, which, rightly studied, may lead to a knowledge of vol- 

 canic action under grander and simpler conditions than have prevailed on the earth 

 during the period of subaerial volcanoes. The author also exhibited a drawing of 

 Aristarchus, showing some undescribed features in the aspect of that, the highest 

 part of the moon's surface. 



' On some Phenomena produced by the refractive power of the Eye,' by Mr. 

 A. Claudet. — This paper was to explain several effects of the refraction through the 

 eye, one of which is, that objects situated a little behind us, are seen as if they were 

 on a straight line from right to left. Another, that the pictures of external objects 

 which are represented on the retina, are included in an angle much larger than 

 one-half of the sphere at the centre of which the observer is placed ; from this 

 point of view a single glance encompasses a vast and splendid panorama extending 

 to an angle of 200°. This is the result of the common law of refraction. All the 

 rays of light passing through the cornea, to the chrystalline lens are more and 

 more refracted in proportion to the angle at which they strike the spherical sur- 

 face of the cornea. Consequently, the only objects which are seen in their true po- 

 sition are those entering the eye in the direction of the optic axis. By this refrac- 

 tion the rays which enter the eye at an angle of 90*^, are bent at 10°, and appear 

 to come from an angle of 80°. This phenomenon produces a very curious illusion. 

 When we are lighted by the sun, the moon, or any other light, if we endeavour to 

 place ourselves in a line with the light and the shadow of our body, we are sur- 

 prised to find that the light and the shadow seem not to be connected at all, and 

 that, instead of being in a line, they appear bant to an angle of 160" instead of 

 180°, so that we see both the light and the shadow a little before us, where they 

 are not expected to be. The eye refracts the line formed by the ray of light, and 

 the shadow and the effect is like that of the stick, one half of which being im- 

 mersed in water, appears crooked or bent into an angle at the point of immersion. 

 This enlargement of the field of vision to an angle of 200°, is one of those innur 

 merable and wonderful resources of nature by which the beauty of the effect is in- 

 creased. .Our attention is called to the various parts of the panorama which ap- 

 pear in any way a desirable point of observation, and we are warned of any dan- 

 ger from objects coming to us in the most oblique direction. These advantages 

 are particularly felt in our crowded towns, where we are obliged to be constantly 

 on the look out for all that is passing around us. 



On the Cultivation of Cinchona in India," by Mr. C. R. Markham. 



Dr. Thompson said it was those only who knew how rapidly the supply of qui- 

 nine from Chili and South America was being exhausted that could know how in- 

 estimable was the work which the paper described. The experiments which had 

 been made had shown, uot only that the plant might be grown in other countries, 

 but that the bark of the young tree yielded a uiuch larger proportion of quinine 

 than that of the old. The good which would result from carrying the cultivation 

 of the plant into new fields was immense ; tor while the application of quinine was 



