THE PROGRESS OF SCIENCE IN THE PAST YEAR. 135 
in darkness gives probability of dry weather from the absence of moisture to 
make rain. A little experience is said to be all that is necessary to make a care- 
ful observer an expert weather-prophet in a very short time. Prof. Piazzi Smith, 
Astronomer Royal for Scotland, during August and September last, fully verified 
the correctness of the predictions made by these instruments. 
In the important field of electric research the interest is growing and the 
inventions claimed are increasing in number. The direction of greatest activity is 
toward the perfection of the light for domestic purposes — that for large halls and 
streets having reached a point where it is no longer considered a problem. For 
private use the incandescent lamp seems to be most desirable and economical. 
The most extensive experiment yet made is that by the Edison Company in 
New York, which has been in operation for the past year in a considerable por- 
tion of the lower part of the city. So far, however, the public have not been 
informed as to cost, the company not having made any statement on that import- 
ant point. And as it is one very vital to them, we will possibly have to answer 
this question, as to the public, by either the extension of the system or a Ifcilure 
to enlarge the area lighted. 
But it seems to be the concurrent judgment of the best informed authorities 
on this subject, that the solution of the problem of domestic lighting by electricity 
depends for general introduction upon the success of experiments now making 
upon secondary batteries. The secondary battery is to be supplied to each house 
and during the day charged to saturation from a central station, sufficient for the 
demand made upon it during the night. The cost by this method, would be very 
much less than by direct supply, while the current would be free from fluctua- 
tions in intensity, which seems impossible by the other method as well as greatly 
reducing risks and expense of breakage in lamps. These secondary batteries on 
the Faure system have been in use on railway carriages in both England and the 
United States. It is, in view of what we know of the genius and ingenuity of 
inventors, safe to say that obstacles will be removed and the electric light, so 
desirable in all respects, become a household servant. 
The scientific world has never been agreed as to the nature or maintenance 
of solar heat. Astronomers and physicists, with the tendency of the intellectual 
age to refer everything beyond our own globe to the phenomena existing here, 
have as a rule regarded the solar heat as due to combustion of the Sun's matter, 
maintained by contraction. This theory has led to calculations, from the mass 
and density of the Sun, as to the ultimate decrease of heat and the extinction of 
planetary life. Or in other words, that at some period in the future the solar 
system is to be one of dead worlds circling about a burnt out central orb. 
Without stopping to characterize this ignoble conception of the infinite pur- 
pose, of a power and wisdom that perfected such a wondrous system amid a uni- 
verse of suns and systems, it may on this occasion not be improper to say that 
this theory has been disputed, and that the debate will not go on entirely upon 
the amount of stoking that may be needed for the solar furnace, or as to where 
the fuel is to come from. — whether its fires are to be fed by its own substance or 
