2S8 PLEASANT WAYS IN SCIENCE. 



" It will be seen," says Mr. Barlow, " that in this con- 

 struction of the instrument the sudden application of 

 pressure is as suddenly recorded, subject only to the modi- 

 fications occasioned by the inertia, momentum, and friction 

 of the parts moved. But the record of the sudden cessation 

 of pressure is further affected by the time required to dis- 

 charge the air through the escape-orifice. Inasmuch, how- 

 ever, as these several effects are similar under similar 

 circumstances, the same diagram should always be obtained 

 from the same pneumatic action when the instrument is 

 in proper adjustment ; and this result is fairly borne out by 

 the experiments." 



The defect of the instrument consisted in the fact that 

 it recorded changes of pressure only ; and in point oi 

 fact it seems to result, from the experiments made with it, 

 that it could only indicate the order in which explosive, 

 continuant, and liquid consonants succeeded each other in 

 spoken words, the vowels being all expressed in the same 

 way, and only one letter the rough R, or R with a burr 

 being always unmistakably indicated. The explosives were 

 represented by a sudden sharp rise and fall in the recorded 

 curve ; the height of the rise depending on the strength 

 with which the explosive is uttered, not on the nature of the 

 consonant itself. Thus the word " tick " is represented 

 by a higher elevation for the " t" than for the "k," but the 

 word " kite " by a higher elevation for the " k " than for 

 the "t" It is noteworthy that there is always a second 

 smaller rise and fall after the first chief one, in the case 

 of each of tht explosives. This shows that the membrane, 

 having first been forcibly distended by the small aerial ex- 

 plosion accompanying the utterance of such a consonant, 

 sways back beyond the position where the pressure and 

 the elasticity of the membrane would (for the moment) 

 exactly balance, and then oscillates back again over that 

 position before returning to its undistended condition. 

 Sometimes a third small elevation can be recognized, and 

 when an explosive is followed by a rolling "r" several 



