MISCELLANY. 



377 



curious and interesting article by a German 

 oculist, showing how the colors of paintings 

 are affected by changes in the eye of the 

 painter. M. Pouchet matches this discov- 

 ery with the curious fact that the lower 

 animals change their own colors through 

 the action of the eye. In a recent work on 

 change of color in Crustacea, this author 

 shows that in fishes, especially the turbot, 

 notable changes of color take place, due to 

 the quantity of luminous rays which fall 

 upon the eyes of these animals. The eye 

 is the point of departure for a nervous 

 shock which is transmitted to the skin, and 

 which finally results in a change, more or 

 less complete, of the color of the animal. 

 This shock, starting from the eyes, is trans- 

 mitted by nerves to the skin ; so that, if 

 certain of these nerves be severed, the ani- 

 mal will become striped with clearly-defined 

 bands, the shock being intercepted by the 

 severed nerves, and transmitted by the 

 others. If the animal is deprived of sight, 

 it ceases to change color, and preserves the 

 same tint, whether it be placed on a black 

 or on a white ground. In the course of his 

 researches at Concarneau, M. Pouchet con- 

 firmed these results in the case of Crustacea. 

 The skin of the frog becomes clearer 

 when the cutaneous nerves are severed. 

 Prof. Goltz, of Halle, shows that primarily 

 the action of the nerves affects the vessels, 

 and that the change in the pigment-cells is 

 a secondary result, and due to a modifica- 

 tion of the circulation. In the active state, 

 these cells are star-shaped, or branching; 

 in repose, they are round. Having removed 

 the spinal cord and brain, if then you sever 

 the nerves leading out to one portion of the 

 skin, that portion will become clearer, the 

 pigment-cells then first assuming the condi- 

 tion of repose. Dr. Witlich thinks this 

 change of color is owing to the decay of the 

 color-bearing cellules, and says it would take 

 place equally in shreds of skin separated 

 from the body. Dr. Mendel, of Berlin, has 

 observed one-sided pigmentation frequently 

 in the insane. 



Observations on the Hydrogen-Flame. 



Besides the phenomena common to ordinary 

 burning, such as luminosity, the disappear- 

 ance of oxygen, and of the substance 

 burned, the production of water and car- 



bonic acid, or some other of the various 

 oxides, there are also certain other phenom- 

 ena that differ with different substances, 

 and that, when known, often become an im- 

 portant means of distinguishing these sub- 

 stances. Thus, burning sodium gives a yel- 

 low flame ; burning potassium, a flame of a 

 purple color ; burning arsenic, a strong odor 

 of garlic ; burning sulphur, suffocating 

 fumes of sulphurous acid, and so on. Burn- 

 ing hydrogen also has its peculiar phenom- 

 ena, which have lately been made the sub- 

 ject of further investigation by Mr. W. F. 

 Barrett, who contributes an interesting ac- 

 count of his researches to a recent number 

 of Nature. 



To study these phenomena to the best 

 advantage, three things, he says, are re- 

 quisite: 1. That the gas be purified and 

 stored in the ordinary way ; 2. That it be 

 led through red or black India-rubber tubing 

 to a platinum, or, better, a steatite jet ; 3. 

 That it be burnt in a perfectly dark room, 

 and amid calm and dustless air. In this 

 way, the flame gives a faint, reddish-brown 

 color, invisible in bright daylight. Issuing 

 from a narrow jet in a dark room, a stream 

 of luminosity more than six times the length 

 of the flame is seen to stretch upward from 

 the burning hydrogen. This weird appear- 

 ance is probably caused by the swifter flow 

 of the particles of gas in the centre of the 

 tube. The central particles, as they shoot 

 upward, are protected awhile by their neigh- 

 bors ; metaphorically, they are hindered 

 from entering the fiery ordeal which dooms 

 them finally to a watery grave. 



Brought in contact with certain solid 

 bodies, the flame gives rise to phosphores- 

 cent effects. Thus, allowing it to play for 

 a moment on sand-paper, and then prompt- 

 ly extinguishing the gas, a vivid-green phos- 

 phorescence remains for some seconds. A 

 similar appearance follows when the flame 

 is directed upon white writing-paper, mar- 

 ble, chalk, granite, or gypsum. 



A much more general effect than the one 

 last mentioned is, the production of a mag- 

 nificent blue image of the flame, that starts 

 up on almost every substance with which 

 the flame is brought into contact. When 

 directed either vertically or sideways, say 

 upon a white plate, or block of marble, 

 there instantly appears a deep-blue and 



