IX.-^ MISCELLANEOUS. 247 



Heliostat and glass prism. Prof. A. S. Herschel. 



97 la. Wheatstone's Apparatus. Paris Observatory. 



971b. Interferential Apparatus, by Arago. 



Paris Observatory. 



3699. Reflecting Stephanoscope. 



Prof. Dr. Lommel, Erlangen. 



(1.) The little apparatus is intended for the observation of interference 

 phenomena produced by a dimmed (triibe) mirror. The mirror is at one 

 end of a short brass tube, which has a lateral excision, and contains a second 

 tube, whose one end is cut off at an angle of 45 to the axis, and is there closed 

 with a plane glass. If the light of a candle is allowed to fall through the 

 lateral apertures upon the plane glass, so that it is reflected vertically to the 

 mirror, it will, on being viewed through the tubes, appear surrounded by 

 Newton's rings, which pass, when the tube is slightly inclined, into the so- 

 called WkewelVs bands. If a pencil of solar rays is caused to enter by the 

 lateral opening, and a lens of large focus is put on to the end of the second 

 tube, the above images can be thrown upon a screen. 



3700. Erythroscope. Prof. Dr. Lommel, Erlangen. 

 The erythroscope is an eye-glass of combined blue cobalt glass with red 



copper-suboxide glass, which gives passage only to the ultra red before 

 line B. Since chlorophyll does not absorb this colour, the green parts of a 

 plant appear, when viewed through the erythroscope, quite light coloured ; 

 the foliage of a tree in sunshine, for instance, will appear as light as a white 

 cloud, and form a light spot upon the dark ground of the sky. 



3701. Melanoscope. . Prof. Dr. Lommel, Erlangen. 



The rnelanoscope, a combination of dark red copper glass and light 

 violet glass, allows chiefly the red rays between B and C to pass, which are 

 absorbed with avidity by plants. Viewed therefore through the rnelanoscope 

 plants will look very dark, almost black. This contrivance and the preceding 

 one show in an instructive manner that plants absorb eagerly the middle 

 portion of the red part of the spectrum, but not at all the ultra red. 



3702. Erythrophytoscope I. 



Prof. Dr. Lommel, Erlangen. 



This combination of Simmler, consisting of blue cobalt glass and dark 

 yellow iron oxide glass, transmits ultra red up to B, and also to yellow-green, 

 blue-green, and blue. Leaves, looked upon through it, appear coral red, the 

 sky blue, the cloud reddish-violet, the soil violet-grey. 



3703. Erythrophytoscope II. 



Prof. Dr. Lommel, Erlangen. 



The erythrophytoscope II. , combined of blue cobalt and light red copper 

 glass, allows, besides ultra red, only blue-green and blue to pass. The effect 

 is similar to that of the preceding combination, only more striking. 



It should be remarked that, only vegetable and anilin green appear, as 

 described under these combined glasses; mineral green would look dark 

 blue-green. 



3704. Coloured Gelatine Leaflets as objects for the spectro- 

 scope. Prof. Dr. Lommel) Erlangen. 



