PROFESSOR ESPY. 31 {. 
several days it may be changed without removing the tube, by turning several 
pints of water into or upon the bottle so as to cause an overflow of most of that 
first contained. Repeating this operation weekly will keep the water quite pure. 
The more nearly filled the tube is with water the less will be the variation due to 
temperature, for it is mainly the expansion of the air m the upper part of the 
tube that depresses the column of water beneath. The change due to atmos- 
pheric pressure is also more marked when the tube is nearly full, since the length 
of the water-column is increased. 
Captain Geo. H. Fay, of Morrison, 111., uses one of these instruments, and 
iby having the tube very nearly filled with water thereby dispenses with the trouble 
•of making corrections for temperature. 
Morrison, III., July 21, 1883. 
PROFESSOR ESPY. 
Few are aware of the origin of the present efficient Signal Service, nor of 
the debt of gratitude the whole country owes to the late Prof. James P. Espy. 
His rise to prominence in the scientific world, as related by Capt. Samuel Erseyis, 
of Philadelphia, who was one of his earliest friends, is one of remarkable interest. 
When about ten years of age, Espy's father died, and mother and son tramped 
from their home near Harrisburg out to Ohio. The boy was put at farm labor, 
at which he served until seventeen years of age, for the meager pay of fifty 
bushels of corn a year. A signal incident marks the commencement of his career. 
Henry Clay was just then rising to fame, and young Espy found himself one 
afternoon within sound of the silvery voice which was yet to captivate its tens of 
thousands. 
Espy was entranced by its witchery and followed the American Cicero as a 
needle the lodestone. He got near enough to Mr. Clay to have some one mor- 
tify him by pointing him out with, " Here, Mr. Clay, here's one of your admirers 
He's seventeen years of age, and can't read." Mr. Clay laid his hand affection- 
ately upon the lad's head and said : " Come, my lad, let us see if we can find a 
book store hereabout." A book store was found, Mr. Clay purchased a copy 
of Noah Webster's speUing book; opened the book at the alphabet, and, pointing 
to the first letter with a long index finger, said : *' This is the letter A. Do you 
understand? Yes ! Well, there are twenty- five more of them. You must learn 
the rest, and when you have learned them it will not take you long to learn to 
read." 
Ten years after this time Espy was here in Philadelphia, engaged in teaching 
school. John .Troutwine, well known to many citizens, was one of Espy's 
pupils. At that time the Franklin Istitute had a high school connected with the 
institution. Walter R. Johnston was the first professor ; his specialty was chem- 
istry. Espy was the second, and taught mathematics. He was hungry for 
knowledge, and the motto prefixed to his first work, "The Philosophy of Storms," 
