436 



SCIENCU. 



[Vol. VI., No. 145. 



noticed signs of fear at an unexpected noise or 

 strange face in the first weeks. Between the 3d 

 and the 10th months, fright is caused more often by 

 auditory than by visual impressions. A child of 

 3i months showed no sign of fear at a conflagra- 

 tion, though surrounded by flames, until the noise 

 of the fire engine was heard, and then he trembled 

 and cried. Thunder terrifies rather than lightning. 

 This is referred to as hereditary and the result of 

 anterior experiences, which have " rather [predis- 

 posed the race to listen for dangers which are near 

 at hand, than to be on the lookout for distant 

 ones." The reverse is true of most animals. 



Finally as an example of the logical powers of 

 infants, that of generalization will serve. Dogs 

 generalize ; they bark at all beggars ; yet they dis- 

 tinguish one beggar from another on nearer ap- 

 proach. A child had a tin box into which he used 

 to delight to stuff things ; he soon found that other 

 of his toys had the power of holding things ; then 

 he tried to find an opening in everything, into a 

 glass stopper because it was transparent ; in short, 

 he had acquired a general idea of an opening. 

 Another child had a canary named ' Koko' ; when 

 he saw chickens in the yard or ducks in the pond, 

 they were ' Koko ' too. While these young children 

 generalize before the acquisition of language, 

 they do not compare. A child was shown a print 

 and stretched out her hands for it ; then a colored 

 print was shown; her joy was beyond bounds. In 

 a second experiment both were shown at once ; she 

 took them for one picture and threw herself 

 towards both ; her attention was not directed to 

 the brighter one. These illustrations are doubtless 

 sufficient to indicate the character of the volume. 



The record of one or two infants is naturally un- 

 satisfactory ; individual peculiarities are certain to 

 enter. What is wanted is a collation and average of 

 many observations. For England, Darwin and 

 Pollock, for France,Taine and Perez, for Germany, 

 Tiedemann, for Austria, Preyer, for Italy, Ferri, 

 have contributed to this study. May we not soon 

 expect to hear as to the psychology of the Ameri- 

 can baby? J. Jastrow. 



LEGAL OHM STANDARDS, 



After the decision of the Paris electrical con- 

 gress of 1884, that the standard resistance, or legal 

 ohm, should be the resistance of a column of 

 mercury of one square millimetre cross-section, 

 and 106 cms. in length, at zero centigrade, it be- 

 came necessary to construct standards that should 

 represent this resistance. In France this task was 

 intrusted by the minister of posts and telegraphs 

 to M. J. R. Benoit; and in England Mr. R. T. 

 Glazebrook, at the request of the electrical stand- 



ards committee of the British association, under- 

 took the same work. 



M. Benoit attacked the question ab initio. From 

 a large number of glass tubes, of about 120 cms. 

 length, and 1 mm. diameter of bore, the four that 

 had the most uniform bores were selected. These 

 tubes were laboriously calibrated to determine the 

 cross-section at every point, and each was then 

 cut off so that the resistance of the column of 

 mercury filling the tube should be as nearly as 

 possible the same as that of the column defined as 

 the standard. The points where the tubes were 

 cut off were determined from the calibration. 

 The resistance of each tube was then calculated 

 from its dimensions, with the following results : — 

 Tube 1 = 0.999999 legal ohms. 



2 = 1.000004 „ 



3 = 0.999979 „ 



4 = 0.999994 „ 



The tubes were then cleaned by passing through 

 them successively strong nitric acid, ammonia, 

 and distilled water ; then filled with pure mercury, 

 and their resistances compared by balancing them 

 against each other in a Wheatstone's bridge. This 

 comparison showed, that, if the mean of the cal- 

 culated resistances be the mean of the true resist- 

 ances, the resistances of the several tubes are as 

 follows : — 



Tube 1 = 1.000018 legal ohms. 



2 = 0.999996 „ 



3 = 0.999959 „ 



4 = 1.000003 „ 



Accepting these as the true resistances, M. Benoit 

 made a number of secondary standards, of glass 

 tubes doubled upon themselves and bent into com- 

 pact forms, and with cups at each end for making 

 contact. The resistances of these tubes, when 

 cleaned and filled to certain marks on the cups 

 with pure mercury, were determined by compari- 

 son with the primary standards mentioned above. 



Mr. Glazebrook considered it unnecessary, for 

 the construction of the required standards, to go 

 through the laborious process adopted by M. Be- 

 noit, for the specific resistance of mercury had been 

 determined in terms of the British association 

 standards, in several elaborate investigations by 

 Lord Rayleigh, Mascart, Strecker, and others, and 

 so based his standards on the value of the resist- 

 ance of mercury adopted by the British association 

 committee; viz., a column of mercury at zero 

 centigrade, one metre long, and one square mm. 

 cross-section, has a resistance of .9540 B. A. units. 



Mr. Glazebrook has made a careful comparison 

 of his legal ohm standards with those made by 

 Benoit, and finds that there is a difference of .0005 

 ohms between them, the Benoit standards being 

 less by that amount. 



