NOTES. 



H3 



which has just been mentioned will convey 

 the voice distinctly when placed against the 

 skull of the hearer, and will even, according 

 to Dr. Thomas, convey audible speech from 

 the skull of one to that of the other. The 

 efforts to make the audiphone and denta- 

 phone useful as regular instruments of hear- 

 ing to the deaf have not had satisfactory re- 

 sults. Dr. Thomas acknowledges that the 

 expectations which have been excited on the 

 subject are likely to be disappointed. Those 

 who are able to hear with the aid of the 

 audiphone hear their own voices perfectly 

 without it ; while those who are unable to 

 hear their own voices without it can hear 

 nothing with it. Dr. Charles S. Turnbull, 

 of Philadelphia, states in the " Medical 

 and Surgical Reporter" that his experience 

 with these instruments has been as nothing, 

 because the suitable cases were so few and 

 far between. The cases in which they have 

 proved of benefit are cases of acoustic deaf- 

 ness, generally due to middle-ear disease, 

 for which devices of the nature of the ear- 

 trumpet generally afford a more satisfac- 

 tory remedy than either of the instruments 

 under consideration. 



Deterioration of Bookbinding by Illu- 

 minating Gas. Professor William Ripley 

 Nichols publishes an interesting paper on 

 the deterioration of the binding of books in 

 libraries, which is commonly ascribed to the 

 action of sulphuric acid supposed to be gen- 

 erated by burning coal-gas. The agency of 

 sulphuric acid having been disputed by Dr. 

 Wolcott Gibbs and others, Professor Nich- 

 ols made investigations to determine the 

 question. Having examined a large num- 

 ber of samples of leather in every stage of 

 decay, he found that morocco was but little 

 affected, common sheep binding was at- 

 tacked, and Russia leather and calf were 

 badly acted upon. An acid taste and an 

 acid reaction were observed that were more 

 marked in proportion as the leather was de- 

 cayed, and sulphuric acid was found in the 

 extract made from the leather with water, 

 in a similarly increasing proportion. Am- 

 monia was also present, in about such a pro- 

 portion as in combination with the sulphur 

 would constitute the acid sulphate of am- 

 monia. Samples of fresh leather gave ex- 

 tracts only slightly acid, not enough so to 

 affect the taste, and contained only a minute 



amount of sulphuric acid in combination. 

 Samples of Russia leather and sheep of 

 good quality yielded from less than a quar- 

 ter to less than a half of one per cent, of 

 acid, and less than quarter of one per cent, 

 of ammonia. A sample of well-worn but 

 not decayed sheep taken from a Bible more 

 than sixty years old, which had never been 

 exposed to gas, gave 1"42 per cent, of sul- 

 phuric acid. Other samples, of very rotten 

 Russia, and of scrapings from a number of 

 books, gave from eight to ten per cent, of 

 sulphuric acid, combined with ammonia. A 

 quantity of rotten leather was carefully ex- 

 tracted with water, and crystals of sulphate 

 of ammonia were obtained from it. It is 

 difficult, in the face of these facts, Professor 

 Nichols urges, to escape the conviction that 

 bindings of Russia, calf, or sheep absorb 

 sulphuric acid when exposed to the prod- 

 ucts of the combustion of illuminating gas. 

 No other condition to which books are com- 

 monly exposed can so well account for the 

 large proportion of acid which was found 

 in the old bindings. It has been objected 

 to this view that sulphurous (not sulphur- 

 ic) acid is the general product of the com- 

 bustion of sulphur compounds; but Pro- 

 fessor Nichols's analyses of the results of 

 the burning of gas have brought out sul- 

 phates with no evidence of the presence of 

 a sulphite. It is admitted to be possible 

 that the disintegration of the leather pre- 

 cedes the absorption of sulphuric acid, and 

 prepares the way for it ; and Professor 

 Nichols intends to make experiments for 

 the determination of this question. 



NOTES. 



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