252 



THE POPULAR SCIENCE MONTHLY 



to make. Cultivated trees had grown so 

 much faster than was expected that peo- 

 ple had been surprised at the growth, and 

 it was now becoming generally known that 

 wood came into profit much sooner than 

 was thought possible years ago, and forest- 

 culture was much more popular in conse- 

 quence. In his State at least 80,000 acres 

 of timber had been planted during the past 

 few years, and the work was still going on. 

 He gave figures as to the growth of indi- 

 vidual species, chiefly from facts within his 

 own observation. Mr. Meehan, from whose 

 Gardener's Monthly we take this account of 

 the meeting, thought that the people, with- 

 out government interference, can be safely 

 trusted with the care of our forests, and the 

 work of reforestation. Individual effort, en- 

 couraged by State laws and agricultural and 

 horticultural societies, would soon replace 

 the decaying forests of our land. 



How the Menopoma casts its Skin. Since 

 reading his " Preliminary Note on the Me- 

 noponia Allecfhaniense of Harlan," before 

 the American Association, Grote has ob- 

 served in the aquarium of the Buffalo So- 

 ciety of Natural Sciences the process by 

 which the menopoma rids itself of its outer 

 skin. This thin and transparent membrane 

 is first seen to loosen and separate from the 

 entire surface of the body, appearing at 

 this stage like an envelope or glove in which 

 the animal is contained. By a number of 

 wide gapings, during which the mouth 

 is opened to the fullest extent, the skin is 

 parted about the lips, and then commences 

 to fold backward from the head. Convul- 

 sive and undulating movements with the 

 body and fore-legs are employed to extract 

 these from the loose skin. The skin then 

 readily falls backward, as the animal crawls 

 forward and out of it, until the hind-legs 

 are reached, when the menopoma turns 

 round upon itself, and, taking the skin in its 

 mouth, pulls it over the legs and tail. The 

 operation reminds one of taking off clothes. 

 The cast-off skin is retained in the mouth 

 and finally swallowed. The operation is 

 quickly performed. 



Poisonous Cooking-Utensils. The dan- 

 ger attending the use of porcelain-lined 

 cooking-vessels was pointed out at a meeting 



of the British Society of Public Analysts, by 

 Mr. Robert R. Tatlock. He stated that the 

 milk-white porcelain enamel with which cast- 

 iron cooking-vessels are now so commonly 

 coated is in the highest degree objection- 

 able, on account of the easy action on it 'of 

 acid fruits, common salt, and other sub- 

 stances, by means of which lead and even 

 arsenic are dissolved out in large quantity 

 during the process of cooking. It was 

 shown that it is not so much on account of 

 the presence of large proportions of lead 

 and arsenic that these enamels are danger- 

 ous, but because they are so highly basic 

 in their character, and are so readily acted 

 on by feebly-acid solutions. He thought 

 that no enamel should be admitted to use 

 unless it was totally unaffected by boiling 

 with a one-per-cent. solution of citric acid, 

 which was a very moderate test. Further, 

 he gave it as his opinion that either the use 

 of such poisonous ingredients as lead and 

 arsenic in large quantity should be entirely 

 discontinued, or that the composition other- 

 wise should be of such a character as to 

 insure that none of the poisonous sub- 

 stances could be dissolved out under ordi- 

 nary circumstances. 



Agencies that formed the Colorado Ca- 

 nons. The great canon of the Colorado is 

 from 3,000 to 6,000 feet deep, through a 

 distance of 200 miles. All the side-streams 

 reach it through profound canons, and each 

 stream has done, and is still doing, its own 

 work of erosion. The process by which 

 these results are brought about is consid- 

 ered by Prof. G. R, Gilbert, in the Ameri- 

 can Journal of Science and Arts, under three 

 principal heads : 1. Weathering ; 2. Trans- 

 portation; 3. Corrasion. 



By weathering, the writer means the dis- 

 integration of rock by the action of tem- 

 perature beating of rain and changes of 

 vegetation. The process, however, would 

 be greatly delayed if the loosened material 

 was allowed to remain and cover the sur- 

 face. Hence transportation becomes a 

 powerful agent in erosion, not only by ex- 

 posing the disintegrating surfaces, but by 

 mechanical wear in the act of removal. 



All rocks are more or less soluble in 

 water, and impurities in the water intensify 

 solvent action. But it usually happens that 



