On the Acceleration of the Saw, &c- 393 
William Maclure, Esq. President of the Society, inas for- 
warded part 1st of Conybeare & Phillips’ Geology of Eng- 
land and Wales, the fourth number of Magendie’s Jour- 
nal de Physiologie experimentale et pathologique, Nos. 44, 
—5—6—7—and—8, of the Revue Encyclopedique, 3 Nos. 
of the Journal de Physique for January, July, and August, 
1822, and also Greenough’s magnificent Geological Map 
of England, all of which have been received. 
Professor Buckland’s splendid work, the Reliquiae Dilu- 
vianae, has also been received from the author. ade 
Omission.—Two valuable boxes of specimens from the 
northern lakes, and various other parts of the United States, 
forwarded by Major Delafield to the Society in 1823, have 
not been acknowledged till now, an omission which was not 
before observed. 
2. Effect of changes of temperature on the impelling power 
of moving water. 
Yors (Pa.) 18th August, 1824. 
To the Editor. 
Sir—A singular circumstance has been. observed in -this 
vicinity lately, which has given rise to considerable dis- 
cussion. The opinions entertained respecting it by those 
who have turned their attention to it, are various ; nor has 
any one been able to account, satisfactorily, for it. This 
induces me to trouble you with a brief narration of it, be- 
lieving that every fact of the kind will be, by you, deem- 
ed worthy to be added to that stock of knowledge, which 
observation has been gleaning and treasuring up for the 
scrutiny of science. 
At the mouth of a creek which empties itself into the 
Susquehannah, a short distance south of the Columbia 
bridge, there stands a saw-mill, which culs an immense 
quantity of timber. The owners, as well as several of the 
workmen who attend the mill, state it.as a fact that at night, 
in the course of a given time, with the same head or quan- 
tity of water, and without any alteration being made in 
the gearing, or machinery of the mill, the saw cuts much 
more timber,than tt does in the same time in daylight ; 
Vou. VIIL—No. 2. 50 
