688 



THE POPULAR SCIENCE MONTHLY. 



the " superheater," which imparts to it the 

 necessary temperature. The iron articles to 

 be acted on are placed in a chamber built 

 of fire-clay, and the steam being admitted 

 to it a coating of magnetic, or black, oxide 

 of iron is produced on the surface. And 

 now for the result. The article has a dull- 

 black appearance, and is susceptible of a 

 high degree of polish. The surface coat- 

 ing is absolutely adherent, and is so hard 

 that it is not removable by ordinary meth- 

 ods, for instance, an iron rasp has no effect 

 on it ; and the same is to be said of all the 

 agents which under ordinary conditions 

 oxidize iron. Salt or fresh water, vegetable 

 acids, and even the London atmosphere, are 

 unable to produce the slightest tarnish. 

 Iron vessels which have contained water for 

 weeks are entirely free from rust. Iron 

 piping and ornamental castings, which have 

 for months lain among the wet leaves in 

 the garden outside Professor BarfiPs labora- 

 tory, are unchanged. The cost of the pro- 

 cess is trifling, less than that of " galvaniz- 

 ing." The sanitary and domestic uses of 

 iron thus prepared are numerous, as for wa- 

 ter-pipes and cisterns and for cooking ap- 

 paratus. 



Plants and Atmospheric Hnmidity. — Two 



questions of considerable interest, viz., that 

 of the effect of living plants on the atmos- 

 phere of houses and that of the relations 

 between forests and atmospheric humidity, 

 appear to have no little light thrown upon 

 them by the ingenious researches of Dr. J. 

 M. Anders, published in the " American 

 NaturaUst." We can not state with any 

 degree of fullness the author's experiments 

 to determine the amount of vapor trans- 

 pired by plants in proportion to the area of 

 their leaf surface. Suffice it to say that ac- 

 cording to these experiments the " Wash- 

 ington elm," at Cambridge, Massachusetts, 

 with its 200,000 square feet of leaf surface, 

 would transpire seven and three quarter 

 tons of watery vapor in twelve diurnal 

 hours of clear weather. Carrying the cal- 

 culation further, a grove consisting of 500 

 trees, each with a leaf surface equal to that 

 of the elm mentioned, would return to the 

 atmosphere 3,8*75 tons of aqueous vapor in 

 twelve hours. In-doors, transpiration is dur- 

 ing the day only about one half as active as 



in the open air, but at night it is about 

 equal in the two situations : hence the trans- 

 piration of a plant in-doors is more than one 

 half as much in twenty-four hours as it 

 would be outside. It follows that growing 

 plants increase the humidity of the atmos- 

 phere in a closed room. This point is very 

 important where rooms are heated by hot- 

 air furnaces. In such apartments the air 

 is drier than in apartments heated by a 

 stove or an open fireplace. In a dry at- 

 mosphere of the temperature of 65° to 68° 

 Fahr. a great demand is made upon the 

 system to supply the air with moisture, the 

 skin and pulmonary mucous membrane are 

 dried, and a condition is induced which is 

 expressed in irritability of the nervous sys- 

 tem, paleness and susceptibility of the skin 

 to cold, liability to pulmonary diseases, and, 

 in short, deterioration of all the functions. 

 Now, if the presence of a certain number 

 of thrifty plants in an occupied apartment, 

 warmed by dry air, would have the effect 

 of raising the proportion of aqueous vapor, 

 it is clear that plants in rooms heated by a 

 hot-air furnace would, in an hygienic point 

 of view, be of very decided value, since they 

 may become the means of obviating very 

 distressing symptoms, or even disease itself. 

 As for the question of the relation of forest- 

 growth to atmospheric humidity and conse- 

 quently to rainfall, such relation would ap- 

 pear to be clearly established by the au- 

 thor's researches. 



Sonrce of Organic Matter in Igneous 

 Rocks. — Associated with the sheet of trap- 

 rock which forms the First Newark Moun- 

 tain, New Jersey, there occurs near Plain- 

 field an amygdaloid trap passing into a met- 

 amorphosed shale. Many of the cavities in 

 the amygdaloid rock are filled with a jet- 

 black carbonaceous mineral, closely resem- 

 bling the " albertite " of New Brunswick. 

 Above the amygdaloid is a metamorphosed 

 shale, traversed by seams and fissures, which 

 are frequently filled with the same albertite- 

 like mineral. Finally, resting on these met- 

 amorphosed beds are slates, shales, and 

 sandstones, which contain fossil fishes and 

 an abundance of obscure vegetal remains. 

 From this state of facts Mr. J. C. Russell 

 (" American Journal of Science " for Au- 

 gust) infers that the organic bodies in the 



