the velocity of sound, made in Holland, 431 
appointment we met with on the first days was however not 
entirely fruitless; we were convinced by it, that none but 
exactly corresponding shots can be of use in determining the 
velocity of sound. The result of the observations of 25th 
and 26th of January, when the reports were heard at one 
station only, and reduced to o° temperature of the centigrade 
scale, and dry air, give differences of whilst the obser- 
vations of 27th and 28th of January, when shots were dis- 
tinctly heard on both stations, had only a difference of 
from each other. 
The time which sound employs to travel from one station 
to another being duly ascertained, we proceeded to measure 
the distance between both stations,. The distances of the 
steeples of Utrecht and Amersfoort, Utrecht and Naarden, 
Naarden and Amersfoort being accurately known, we mea- 
sured angles on our stations between these steeples, and on 
each steeple between the other steeples and the stations. 
Thus the distance was calculated by four different triangles, 
and the greatest difference between these calculations was 
2®, 45 or 8 feet, which appeared of no consequence in these 
experiments. The distances of the different steeples which 
we took for our basis, result from the very exact geometrical 
survey of General Krayenhoff.* 
From these different data we found, by calculations of 
which the detail will be given hereafter, that in our experi- 
ments at a temperature of 32° Fahrenheit, or o° of the cen- 
tigrade scale, the velocity of sound is 332® ,049, or 1089,7445 
English feet per sexagesimal second. A table showing the 
* Precis des Operations Geodesiques et Trigonometriques en Hollande, par le 
G6n6ral Krayenhoff. 
