166 Bibliography. 
“On the 2lst, the weather became unsettled, with light westerly winds, and 
we made but little progress to the westward, The barrier, at 6 Pp. m., was seen 
trending to the westward. In consequence of indications that (iedeed bad 
weather, I deemed it useless risk to remain in the proximity of so many ice- 
islands; and a strong breeze, with squally weather, having already set in, I took 
advantage of it, feeling satisfied that our farther continuance in this icy region 
would not only be attended with peril to the ship, but would cause a waste of the 
time which was demanded by my other duties; and having nearly three thousand 
miles to sail to our next port (Bay of Islands), I made up my mind to turn the 
head of the vessel northward. 
“‘T therefore had the officers and crew called aft, thanked them all for their 
exertions and good conduct during the trying scenes they had gone through, con- 
gratulated them on the success that had attended us, and informed them that I had 
determined to bear up and return north. 
“ Having only twenty-five days’ full allowance of water, I ordered its issue to 
be reduced to half allowance. 
‘“‘ J have seldom seen so many happy faces, or such rejoicings, as the announce- 
ment of my intention to return produced. But although the crew were delighted 
at the termination of this dangerous cruise, not a word of impatience or discontent 
had been heard during its continuance. Neither had there been occasion for 
punishment; and I could not but be thankful to have been enabled to conduct 
the ship through so difficult and dangerous a navigation, without a single accident, 
with a crew in as good a condition, if not in a better, than when we first nentineat 
the icy barrier. For myself, I deed felt worse for the fatigues and anxieties 
I had undergone; but 1 was able to attend to all my duties, and considered myself 
amply repaid for my impaired health by the important discoveries we had made, 
and the success that had attended our exertions.” 
2. Prof. W. R. Johnson on the Heating Power of various Coals.— 
In the last volume of this Journal, p. 394, we gave a brief notice of the 
elaborate and valuable ‘‘ Report” made by Prof. Johnson to the Navy 
Department, detailing the result of a long series of experiments insti- 
tuted by him under the authority of government, upon the American 
coals, as well as some foreign ones. We take the following resumé 
of his labors from a report submitted to the Academy of Natural Scien- 
ces of Philadelphia, and published in their Proceedings for February, 
1845, p. 202. 
Prof. Johnson first enumerates some of the methods which have been 
hitherto employed by chemists and others, to ascertain the relative 
heating powers of fuel. . 
1. The heating of water, without converting it into vapor, as praetiued 
first by Rumford, and more recently by other experimenters, particu- 
larly by Despretz and Dulong. The French chemists assume as the 
unit of calorific power, 1 gramme of water heated 1° centigrade, (1°°8 
Fahr.) The number of such units produced by burning 1 gramme of 
combustible is termed its calorific efficiency. 
2. The melting of ice, as in the calorimeter of Lavoisier and Laplace, 
also employed by Hassenfratz. The heat of fluidity (185° Fahr.) is 
here the measure of effect. 
Ow 
