204 
only in a certain atmosphere, and this at- 
mosphere is to be found only where scien- 
tific work is going on. Some little corner 
of time can always be found even by some 
of the most overburdened of us, and as to 
equipment, it should not be forgotten that 
the scientific appliances at command of the 
school teacher of the present day are greatly 
superior to those of the average college man 
of a generation ago, and are not greatly be- 
hind those of the average college man of 
the present. Yet there was great scientific 
activity in certain localities at a time when 
laboratories, as we know them, had not yet 
come into existence. Men are still living 
who can remember when the first chemical 
laboratory in Germany was established by 
Liebig, and one need not to be very old to 
look back upon the beginnings of labora- 
tory instruction in this country. 
Qualification for research must always be 
acquired by individual effort. Any one 
who is really fit to teach science has at 
least the latent gift necessary to the inves- 
tigator. To develop the gift he must, how- 
ever, cultivate the habit of scientific read- 
ing and the habit of experimentation. The 
number of science journals is now so great 
that no one can longer pretend to read them 
all; but we have in the admirable summary 
entitled, Science Abstracts, and in Wiedemann’s 
Beiblitter, the results of the whole world of 
physics presented in brief form. One of 
these two journals should be taken by every 
physics teacher, and in addition he should 
subscribe to and read some one of the 
standard journals devoted to his subject. 
Given a well-developed habit of experi- 
mentation, it only remains to select some 
topic and to study that persistently to the 
point of obtaining definite results before 
taking up another. A1Il subjects for inves- 
tigation are not equally within the reach 
of the teacher in the secondary schools. 
We can not, for example, expect to dupli- 
cate in our laboratories the thousands of 
SCIENCE. 
[N.S. Vou. XIII. No. 319. 
storage cells necessary to the carrying on 
of the researches upon which Professor 
Trowbridge, of Harvard University, is en- 
gaged, nor to lay out large sums for appa- 
ratus of any other kind. As a rule, the 
apparatus necessary to an investigation is, 
however, not very expensive ; certain stand- 
ard instruments, such as the balance, the 
thermometer, the spectroscope and the gal- 
vanometer, are to be found in every de- 
cently equipped school at the present day, 
and work of the highest interest can be 
done by supplementing these with special 
apparatus which may be either home-made 
or may be obtained at a small cost by em- 
ploying our ordinary artisans. 
The following suggestions of topics for 
research which may be pursued without 
elaborate or unusual apparatus in the spare 
time of any one who possesses the intense 
love of experimentation, characteristic of 
the true man of science, may serve to show 
that there is no lack of material within the 
reach of every ambitious physics teacher. 
The temperature at which pure water 
reaches its maximum density has been care- 
fully determined, and it is known that the 
introduction of a gas such as ammonia, 
which is largely absorbed by water, or of a 
salt in solution like sodium chloride, or of 
aleohol or sulphuric acid, not only lowers 
the freezing point and changes the density 
of the liquid, but that the point of maximum 
density falls, as the amount of added sub- 
stance is increased, more rapidly than the 
freezing point itself; until finally the phe- 
nomenon of maximum density disappears 
altogether. Any one who possesses a good 
thermometer reading to low temperatures 
or who has sufficient skill and experience 
to make and calibrate a thermo-junction 
can .readily extend this investigation to 
solutions and mixtures not yet studied. 
The only instruments required for such in- 
vestigation, aside from the usual laboratory 
utensils, are a good thermometer and a 
