130 M. C. Thiseng— Velocity of Sound in Wood. 
second. Removing the stopper to a ventral segment dimin- 
TABLE IV. 
Velocity of sound in American woods : measured by the Graphic Method. 
Names of Wood. Length, Sp. Gr. Temp. Velocity. eo 
Cedar, No. }, 1836° mm | 0-432 21°5C.| 3797-2 Mm) 356M 
ue 2, 1838°4 "482 20°9 | 4073°89 | 9°99 
¥ 3, 1838-75 465 28° 3864-79 | 5:00 
“ 4, 1836°72 417 ae 4161-65 | 5°62 
‘ 24, 65 478 18°8 5°89 
White Wood, 6, 1838°57 476 22°4 4927°30 | 1:43 
* % fi 1834°0 3 19°8 5201-22 | 873 
ae es 10, 1142°37 478 180 | 4650°60 90 
«. Pine, 13, 18. 490 20° | 4713°36 | 663 
H xt 15, 1841°9 432 20°0 4522-46 | Tl 
-. Ae : 1 544 27-0 4282745 | 5°52 
sae S otic ; 1838-26 541 27-3 4261°51 | 5°88 
' : , 562 21-2 365741 | 4°96 
Mahogany, ; 1349°1 540 20°0 | 4135°26 | 5°39 
Black Walnut. : 1378°63 518 191 | 4780-72 60 
erry, ,, 1560°1 693 | 18-0 549 
Yellow Pine, , 1052°45 664 20°2 427448 | 5°60 
L Oak, i, 1 650 25°0 | 4179°80 | 5°34 
White Oak, 3, 1494°5 175 | 26-0 | 431650 | 487_ 
There were, however, certain difficulties to contend with 
which will now be briefly mentioned. I had not long been 
engaged upon this work, when I discovered a tendency to ver 
tical transverse vibration in some of the rods, thus carrying the 
pointer off the plate. To meet this difficulty a kind of holder 
was contrived and covered with felt which, while only touch- 
ing the rod lightly, held-it in position. This damper wa 
placed in various positions along the rod, and the correspond- 
ing rates of vibration measured. These values were tabu 
for the several positions shown in fig. 2, which were as follows: 
K, as near the end as possible; D, 400™™ from E; 0,7 
