Scientific Intelligence. 187 



membrane, distinct, and rather thicker than natural. The retina was 

 unchanged ; the solid body within was marked by the same depres- 

 sion which had been observed externally. It was of a pale white 

 color, and was internally of a cellular texture, like the cancelli of the 

 long bones. The crystalline was indurated and of a yellowish white 

 color ; the optic nerve was wasted. — Idem. 



9. Zoological Weather Glass. (Mag. of Nat. Hist. IV. 479.) — 

 At Schwitzengen, in the post house, we witnessed for the first time, 

 what we have since seen frequently, an amusing application of zoo- 

 logical knowledge, for the purpose of prognosticating the weather. 

 Two frogs, of the species Rana arborea, are kept in a glass jar about 

 eighteen inches in height, and six inches in diameter, with the depth 

 of three or four inches of water at the bottom, and a small ladder 

 reaching to the top of the jar. On the approach of dry weather the 

 frogs mount the ladder, but when wet weather is expected, they de- 

 scend into the water. These animals are of a bright green, and in 

 their wild state, here climb the trees in search of insects, and make 

 a peculiar singing noise before rain. In the jar they get no other 

 food than now and then a fly, one of which we were assured, would 

 serve a frog for a week, though it will eat from six to twelve in a day, 

 if it can get them. In catching the flies, put alive into tlie jars, the 

 frogs display great adroitness. — Idem. 



ARTS. 



1. Manufacture of Red Crayons, for Drawing. — Pulverize a 

 certain quantity of hematite in porphyritic or other hard mortar, ming- 

 ling it with filtered water, so as to reduce it to an impalpable powder. 

 This is to be diluted with a sufficient quantity of water to allow the 

 finest portions of the mixture to pass through a fine seive, placed 

 over a vessel of water. The liquid holding the hematite in suspen- 

 sion, is agitated and left in repose for twenty four hours ; the water 

 is then decanted cautiously, and the fine powder remains at the bot- 

 tom. This is to be incorporated with gum arable, or isinglass, in 

 proportions, varying according to the use to which the crayon is to 

 be applied, viz : 1. For those of a tender quality, which leave large 

 marks, eighteen grains of dry gum arable, to one ounce of well pre- 

 pared hematite. 2. For harder crayons, destined for small delicate 

 strokes, twenty two grains of gum to one ounce of powdered hematite. 



