494 J. J. Minot—Spark Adjuster for the Holtz Machine. 
eter. The weights, which are necessary to keep the index of 
the balance at zero, when the level of the water in the outer 
vessel falls through the millimeter divisions on the graduated 
tube, are noted. The upward pressure of the water, and conse- 
quently the tension upon the suspending cord, are then given in 
was lowered, the following: 
Immersed at 110 mm, Weight = 2 grams. 
6c 102 “cc “ 2°5 “cs 
“ 93°5 “6 ““e 3°0 “ 
“ 85° Ts 35 
“ce 76°5 “ “cc 4 0 it4 
es 6775 ; 4:5 
6 60° “« 3 50 
66 43 0 6s if 5'D “ 
In these experiments a fall of 8-1 mm. corresponded to a dif- 
ference of 5 of a gram. It is evident by increasing the size of 
the outer vessel that a large amount of water would measure a 
slight displacement. When the cord was set in vibration, the 
following results were obtained : 
aS a mi ani 
110 2° 6 
84 3°5 5 
76 4- Q 
30 6°7 3 
The ratio of the numbers in the second and third columns 
will be found to follow Melde’s law. 
For qualitative or quantitative experiments upon beats or 
Lisajous curves this method of loading the prong of a tuning 
fork can advantageously replace the bit of wax or the sliding 
weight, since we have at our command a quick and precise 
method of adjustment. 
No. VIL—A Spark Adjuster for the Holtz Machine; by JAMES 
J. Mrtnort. 
In the Annalen der Physik und Chemie, Bd. 137, s. 452: 
and Bd. 139, s. 509, under the title of “ Schwache Elektrische 
Funke in Luft., von P. Riess,” a method is described of obtain 
ing different kinds of electric sparks from the Holtz machine. 
