856 



THE POPULAR SCIENCE MONTHLY. 



ceoua variety), perhaps from one to many 

 centuries ; coarse fossiliferous limestone, 

 twenty to forty years ; fine oolitic (French) 

 limestone, thirty to forty years ; fine oolitic 

 (American) limestone, untried here; coarse 

 dolomite marble, forty years ; fine dolomite 

 marble, sixty to eighty years ; fine marble, 

 fifty to two hundred years ; granite, seventy- 

 five to two hundred years ; gneiss, fifty 

 years to many centuries. Many of the best 

 building-stones in the country have never 

 yet been brought to the city. 



Peroxide of Hydrogen,— Peroxide of 



hydrogen, though it was discovered in 1818, 

 has only recently, by the aid of cheapened 

 processes of preparation, come into general 

 use. When pure, it is a colorless liquid, 

 which in decomposing gives off four hundred 

 and seventy-five times its volume of oxygen. 

 Diluted solutions of it, kept in the dark 

 at a temperature of not more than 80°, may 

 be preserved for a very long time without 

 decomposing. It is obtainable pure, in 

 large quantities, and cheaply, in solutions 

 of three per cent by weight or ten per cent 

 by volume ; and it has come into extensive 

 use as a bleaching agent, for disinfection, 

 household purposes, and the toilet. It is 

 the really operative agent in air-bleaching 

 on the grass, which has been in use from time 

 Immemorial, and is well adapted for bleach- 

 ing substances of animal origin, in which 

 chlorine agents often fail. In using it the 

 substance to be bleached must first be care- 

 fully cleansed from dirt and oil. It may 

 be applied as a bath in the shape of a 

 weakly acid solution neutralized with a few 

 drops of ammonia, or the substance may be 

 dipped in it, and afterward slowly dried in 

 the air. As the water evaporates, the con- 

 centration of the peroxide of hydrogen in- 

 creases, and the bleaching goes on more 

 energetically. Dumas and Pettenkofer have 

 applied peroxide of hydrogen with much 

 success and satisfaction to the clean- 

 ing of oil-paintings and engravings. This 

 substance has recently been found to be 

 one of the most valuable and effective dis- 

 infecting agents. In the household it has 

 proved to be equal to the best of other 

 known substances for purposes of washing 

 and cleansing the person. It is adapted to 

 the most tender skins. It has been pro- 



nounced preferable as a tooth-wash to all 

 powders and to all other preparations which 

 do not depend upon it. In bathing, with 

 the addition of a drop or two of hartshorn, 

 it quickly disintegrates and removes the 

 dead skin without affecting the living tissue, 

 except to make it more healthy and hardy. 

 It is a salutary hair-wash, provided the hair 

 has been prepared for it by previous wash- 

 ing with soap or spirit. Professors Alex. 

 Classen and 0. Bauer have found it a pow- 

 erful agent in analytical chemistry. — Die 

 Natur. 



Fact and Fancy regarding Fingal's Cave. 



— At the Montreal meeting of the American 

 Association in 1882, Mr. F. Cope Whitehouse 

 offered a paper on " The Caves of Staffa, 

 and their Connection with the Ancient Civ- 

 ilization of lona." The Committee on Pa- 

 pers, having heard Mr. Whitehouse in ex- 

 position of his views, and examined his 

 maps and drawings, and the testimonials 

 which he was able to produce from men of 

 authority in science, adjudged that there 

 were sufficient merit and originality in his 

 paper to justify giving it a hearing. The 

 article was also regarded by us of enough 

 interest to be given to the readers of 

 "The Popular Science Monthly" in De- 

 cember, 1882; and a summary of it was 

 published in " Notes and Queries," Decem- 

 ber 28, 1883. In it the author, regarding 

 the situation of the Island of Staffa, which 

 is shown in the map, the character of its 



rocks, the form of Fingal's Cave, and the 

 shape and direction of its exposure, con- 

 cluded that it was extremely unlikely that 

 the cave could have been hollowed out 

 by the natural action of the waves, and 

 suggested the question whether it might 

 not have been artificially excavated. The 

 paper has not yet been adequately an- 



