RECENT PROGRESS IN ELECTRICITY. 
169 
brication, absence of vibration and yet high rotative speed-— 
even a conservative engineer like myself may feel justified 
in saying definitely that the days of the steam-engine are 
numbered. When we consider that with steam turbines not 
less than eight times the power can be generated in a given 
space than can be produced with steam-engines, that the 
consumption of coal is considerably less, that the cost of the 
electrical apparatus is only one-third or less, and that the 
regulation is better, we need no aid of the spirit of prophecy 
to see that the expiration of the patents will be followed by 
an almost immediate and general use of this device. 
The projects for the thermo-electric generation of elec¬ 
tricity by thermopiles and by carbon in melted alkaline 
salts, which attracted so much attention last year, have 
given no practical results and nothing more has been heard 
of them. 
Tide motors have been used with some slight success, but 
commercially the first cost has stood in the way and will 
probably continue to do so. New devices for the utilization 
of aerial energy by windmills of constant angular velocity 
have been proposed. To touch the matter with the point of 
a needle, all such attempts to use the intermittent forces of 
nature must be at present a failure for lack of cheap means 
of storing energ} r . Consider, for example, the case of the 
storage battery. A wind or sun motor may easily be inoper¬ 
ative for a week. Hence a plant selling one horse-power 
hour of work per day must be capable of storing up at least 
six horse-power hours. A storage battery to store up six 
horse-power hours of energy would have cost, a few years 
ago, $600, but now only about $300. Twenty per cent is 
the usual depreciation, but assuming it is only 10 per cent, 
and interest at 5 per cent, gives us a yearly fixed charge of 
$45 for these items. Now 2 cents per horse-power hour is 
a large profit over working expenses and fixed charges on 
an electric plant for distribution, but assuming this, we get 
a revenue of only $6 per year, leaving a debit of $39 per 
year for each horse-power hour of plant. 
