FEBRUARY 15, 1884.] 
is exerted on the supports of the currents, and 
not on the currents themselves. But, however 
we may explain the experiment, it follows that 
a magnetic field in the stationary state develops 
an electromotive force which tends to move 
electricity in the direction of the electro-mag- 
netie action; that is, to the left of an observer 
placed in the current, and who is looking in 
the direction of the magnetic force.’’ Perhaps 
one cannot do more than make the above state- 
ment in the present state of our knowledge ; 
but the fact that the phenomenon in question 
is different in different metals shows the in- 
fluence of the supports. In general, we like 
the arrangements of the topics treated better 
than that of Maxwell; and we hope that this 
book marks the revival of a period of graceful 
and lucid treatises on mathematical physics 
which we have a right to expect from French- 
men. 
The English translation of this work by Dr. 
Atkinson is well executed, and is revised by 
the authors, who have added certain portions 
to it which are not contained in the French 
treatise. We have noticed here and there 
faults in punctuation which add to the difficulty 
of comprehending certain relations. 
LARISON’S TENTING-SCHOOL. 
The tenting-school: a description of the tours taken 
and the field-work done by the class in geography, 
in the Academy of science and art at Ringos, 
N.J., during the year 1882. By C. W. Lart- 
son, M.D., principal of the academy, etc. Rin- 
gos, N.J., Larison, 1883. 292 p. 12°. 
Tuis is an amazingly queer little book, — so 
full, indeed, of oddities, that one is at a loss 
where to begin an account of them. In the first 
place, the author is evidently one of our orthoe- 
pomaniacs. Nearly all the vowels, and many of 
the consonants, are decorated with diacritical 
points. The result is, that the pages have 
a singularly bristling and formidable aspect. 
But we advise the reader to discipline his eye 
to this painful amelioration of the written 
speech, for a reward awaits him. Behind this 
printed ‘ chevaux-de-frise’ there is a lot of 
things worth reading. The first effort of the 
author is to tell just how he managed for the 
conveyance and camping ofa party of students, 
boys and girls. Every little detail for the 
construction and equipment of a wagon and 
camp for eighteen persons is carefully set forth. 
The most trifling articles are figured in rude 
woodcuts. All this, though in its way useful, 
would be tedious but for the naive though 
often cumbrous language in which it is given, 
SCIENCE. 203 
and the strangely complicated ways of meeting 
simple needs. When, for instance, he comes 
to the making of the camp-fire, which the un- 
tutored campaigner accomplishes as best he 
may, our author tells his very ingenious way. 
The plan is so altogether good, that we give 
it in full, unhappily omitting the diacritical 
accents, which are beyond the resources of 
an ordinary press. 
‘*To kindle fire, we use a kind of strong iron cup, 
fastened to an iron handle about three feet long. 
This cup is very wide at the top and will hold about 
a quart. In this cup, we place a handful or more of 
resin, a gill or more of kerosene, and about a table- 
spoonful of a mixture, consisting of one part of ether 
and four parts of alcohol. At first thought, this may 
seem to be avery incompatible mixture; but, of its 
practical value, we have much evidence. ‘To start a 
fire in wet wood, during a rainy day, under ordinary 
circumstances, is not easy; but with the arrangement, 
and the fuel above named, it is readily effected. 
‘* To ignite resin, in the open air, with an ordinary 
match, is almost impossible. To ignite kerosene in 
the open air with a match, is not easy; and to fire alco- 
hol in an open pan, with a match, is not done at every 
trial. Each of these substances require (sic) to be 
heated up to a certain point, —the kindling point, 
before they will ignite. To raise the temperature of 
either of these to the kindling point, requires more heat 
than is developed by the burning of a match; but, 
ether is so volatile, that when poured out, its vapor 
instantly rises. This vapor fires at so low a tempera- 
ture, that when a burning match is brought in con- 
tact with it, it ignites with explosive violence, and 
continues to burn with vigor until consumed. While 
burning, the heat generated, evaporates the alcohol, 
raises the temperature of the alcoholic vapor to the 
burning point, and ignites it. By the burning of the 
alcohol, the kerosene vapor is raised to the kindling 
point, and is ignited. The burning of the kerosene 
soon develops heat enough to liquify (sic) the resin, 
evaporates it and ignites it. At this juncture, a part 
of the kerosene and resin begins to be converted into 
a gas that makes a hotter blaze than that made by 
burning either kerosene or resin alone; besides, at- 
tending this fire is much less smoke than is made by 
the burning of resin alone. 
‘““The cup of burning kerosene and resin, when 
placed under a heap of wood that is not too wet, soon 
raises the fuel to the kindling point, ignites it and 
gives to the fire such impetuosity that it makes water 
boil quickly, and butter to fry and sputter furiously. 
‘* With the cup alone, charged:as above directed, I 
have boiled a two gallon tea kettle of water in eight 
minutes. But, this could not have been done in a 
windy day. 
‘*Tt would be criminal to make the above state- 
ment, respecting the iron cup and the fuel to be used 
with it, without informing the tiro that it is very 
dangerous. Should any one attempt to use it, he 
cannot be too careful. The act of touching it off 
with a match, unless circumspectly done, may prove 
very disastrous. The results of using this mixture 
without sufficient cireumspection we have seen. Suf- 
fice it to say, they were terrible.”’ 
Unhappily, our author does not give a pic- 
ture showing the effects of these occasional 
catastrophes on the camp of innocents; but 
