194 



MEMOlliS OP THE NATIONAL ACADEMY OF SCIENCES. 



ill 1877, tlif (late of the report, .so tliat it is certain that a considerable numlier of tlie pupils born 

 between lS4(t and 185!> were married after the date of tbe report, and .so escaped euinueratiou. It 

 is questionable, however, whether this eonld alfect the proportion who were married to deaf-mutes. 

 It is more reasonable to suppose that in iliis (lase the apparent decrease is real, for an entirely 

 different method of investigation leads to a siniihir result. In the years 184.':!, 18.57, 1867, and 1877 

 the directors of the American Asylum published in their re[)orts the statistics of the institution, 

 giving the names of those ]>ui>ils who had married. If we assume that the pupils who were not 

 recorded as married in the 1843 report, but who were recorded as niaiTied in the 1857 report, were 

 married between the years 184.*? and 1837, &c., we can divide the marriages reported from tbe 

 American Asylum into four classes: (1) Marriages contracted before 1843, (2) marriages contracted 

 between 184.'') and 1857, (3) inariiages contracted between 1857 and 1867, and (4) marriages con- 

 tracted between 1867 and 1877. The results are shown in the following table: 



Table XXIII. — Marriages of the pvpih of the American Asylum. 



In this case we find that although the number of pupils presumed to have married between 

 1867 and 1877 is greater than the number who married in the preceding decade, the proportion 

 who married deaf-mutes is less. 



It is evident from a comparison of all the tables that of the deaf mutes toho marry at the present 

 time not less than 80 per cent, marry deaf mutes, ichile of those who married during the early half of 

 the present century the proportion who married deaf-mutes was much smaller. 



It is of course a matter of importance to ascertain to what extent congenital deaf-mutes 

 intermarry, but unfortunately the institution records are too imperfect to allow us to draw con- 

 clu.sions on this point. Six hundred and fifty-four pupils of the American Asylum and Illinois 

 Institution are each recorded simply to have "married a deaf-mute," without one word of expla. 

 nation as to the name of the deaf-mute or the cause of deafness.* 



It will thus be understood that the records of deaf-mute marriages are very imperfect, and it 

 is to be hoped that some of our large institutions may publish fuller information concerning them. 

 In the case of a deaf-mute partner it should be stated whether the deafness was congenital or not. 



* Since the reading of this paper it occurred to nie that some light might be thrown upon the subject by the 

 theory of Probabilities. I therefore 8ul)iiiitted the question to Prof. Simon Newcomb, who not only agreed with me 

 in this idea, but was kind enough to present a solution of the problem deduced from the data given in this paper. 

 He thinks the most probal)le conclusion to be this: 



1. Of the congenitally deaf who ni:irricd deaf-iuntes oue-half married cougenitally deaf and one-half uon-cou- 

 genitally deaf. 



2. Of the non-congeuitally deaf who married deaf-mutes three-sevenths married cougeuitally deaf aud four- 

 sevenths uon-congenitally deaf. 



The full text of Professor Newcomb's letters will be found iu Ap|)eudix Z. 



