Juxe 5, 1885. 



SCIENCE 



461 



had presented its broadside to the launch. 

 As the boat approached bow on, it corresponded 

 to a target somewhere about six feet square, 

 presenting a convex surface to the impinging 

 sound-wave. Even in this case a feeble echo 

 was perceived when the boat was at a con- 

 siderable distance (estimated to be nearly one- 

 quarter of a mile). That an} r echo should 

 have been perceived at all under such circum- 

 stances, was a surprise. The sound was heard 

 only by the closest attention, but in the case 

 of larger vessels the effects were very distinct 

 and striking. 



Experiments were made which demonstrated 

 the fact that the speaking-trumpet attached to 

 the gun was of material assistance in giving 

 direction to the sound-impulse, and in inten- 

 sifying the audible effect. 



Mr. Delia Torre claims that a steam-whistle 

 or siren, combined with a projecting apparatus 

 like a speaking-trumpet, will prove as efficient 

 as the gun. 



During the experiments on the Patapsco 

 River, a curious rumbling effect, like the roll- 

 ing of thunder, was often observed, which con- 

 tinued for some seconds. A similar sound 

 was also noticed, as an echo from a well-wooded 

 shore ; but the effect alluded to above could 

 not have been due in any wa} 7 to the land, as 

 the sound commenced immediately upon the 

 firing of the gun, whereas the shore was dis- 

 tant at least a mile or a mile and a half. 



The sound was probably due to the presence 

 of ripples on the surface of the water, as the 

 effect was much less marked when the surface 

 was smooth. Such a sound might prove a 

 disturbing element of importance in a rough 

 sea, but would hardly be sufficient to prevent 

 the detection of an echo from a large iceberg. 

 Had shots been fired periodically from the 

 bow of the City of Berlin, it can hardly be 

 doubted that the presence of an obstacle ahead 

 would have been discovered in time to prevent 

 the collision that actually occurred. 



Alexander Graham Bell. 



SOME PECULIARITIES IN THE AGE STA- 

 TISTICS OF THE UNITED STATES. 



Shortly after the issue of the present cen- 

 sus reports, attention was called to the pecul- 

 iar fact that very many more persons were 

 recorded as being just 20 or just 50 years old 

 than were as being 19 or 49. It is easy to 

 see that there ought to be more persons living 

 at any one year of life than at the next, — 

 more at 7 than at 8 years of age, more at 19 



or 49 than at 20 or 50. Of all the infants less 

 than a month old at the present moment, quite 

 a large number will die before completing their 

 first year; many of those then surviving will 

 die before the end of their second year ; and 

 so on, there being fewer left in each year than 

 in the preceding year. 



But all this is true only when certain con- 

 ditions are satisfied. The growth of the pop- 

 ulation, it is assumed, is by natural increase 

 alone, or nearly so. The number of foreign- 

 born inhabitants, for instance, between the 

 ages 10 and 15, will be smaller (that of native 

 Americans, of course, very much larger) than 

 the number between the ages 20 and 25, 

 because so very many of the immigrants are, 

 on arrival, between 20 and 25 years old. So, 

 too, a war, or an epidemic which is particularly 

 fatal to persons between certain ages, might 

 be the cause of an exception to the general 

 rule, at least until the generation so affected 

 had died out. 



But the effect of any such circumstances on 

 the census figures which are here dealt with, 

 may, without hesitation, be regarded as insig- 

 nificant. The preponderance of the number 

 of persons at the ages containing round num- 

 bers, over the number at the age immediately 

 preceding (this being rather an ' odd ' number) , 

 must be ascribed to an entirely different kind 

 of influence. 



Before going farther, it is necessary to ap- 

 preciate how enormous the attraction towards 

 round numbers really is. Very naturally this 

 attraction is greatest towards the ages contain- 

 ing multiples of 10, for then the numbers are 

 ' roundest.' Subtract the number of persons 

 recorded as 9 years old from the number re- 

 corded as 10, and express this excess in per- 

 centage of the number at 9 years. Do this for 

 the excess of the number at 20 over the num- 

 ber at 19, of 30 over that at 29 ; and so on, 

 the last being the excess of the number at 90 

 over the number at 89 years of age. The 

 average of the 9 percentages thus obtained 

 is what I will call the average ' 10 exaggera- 

 tion,' any one of the percentages of which it 

 is composed being spoken of as the • 10 exag- 

 geration ' at 20 or 30 or 60 3-ears, as the case 

 may be. This average for the total population 

 of the United States is 71J % ; and the several 

 percentages of which it is the average vary 

 from 9.5 % to 1 26 % . This means, that instead 

 of finding fewer persons recorded at any such 

 'round' age as 20, 30, etc., than at the age 

 immediately preceding (19, 29). you would 

 find, on the whole, nearly If times as many. 

 You might find only l T \j- (an excess of 9.5 %) 



