644 
Notices of Books. 
[September, 
speculations are to him, the truth is dearer, and according as 
they consort or do not consort with it, does he expedt others to 
give them entertainment, or undertake to denounce and repudiate 
them himself.” 
Navigation and Nautical Astronomy , with Special Table , 
Diagram , and Rules adapted for Navigating Iron Ships. 
By the Rev. W. T. Read, M.A. London: Elliot Stock. 
1879. 
An useful work containing many original examples, and well 
adapted for teaching young naval officers the first principles of 
navigation. 
The Electric Light in its Practical Applications. By Paget 
Higgs, LL.D., D.Sc. London: E. & F. N. Spon. 1879. 
This work is specially devoted to a description of the various 
attempts which have been made to obtain a practicable system 
of elecftric lighting. An introductory chapter on the general 
principles of the voltaic arc and the method of lighting by 
incandescence is followed by chapters on eleCtric lamps and 
candles ; magneto and dynamic machines and their efficiency, 
and eleCtric regulators ; the division of the eleCtric light is briefly 
discussed, and finally the commercial aspeCt of the question, 
and the various applications to military, maritime, mining, and 
other purposes. 
In the first chapter the avoidance of waste of light is much 
insisted on, and the author asserts that when the laboratory of 
the Sorbonne was first lighted by elecftric candles “ at least one- 
half of the light produced ” was lost by radiation towards the 
sky through the glass roof of the building which served to light 
it during the day. The loss by this means in the case of an 
open-air light exposed at a considerable elevation, and un- 
furnished with refleCIors, must be enormous. In the second 
chapter the various voltaic-arc lamps are described and figured; 
the last-mentioned of these — Higgs’s lamp — is said to produce, 
with only four ordinary Bunsen elements, sufficient light to 
illuminate a building 60 feet by 40, and, when worked by a 
dynamo-eleCtric machine of 2 \ horse power, to produce four 
lights each equal to 400 candles. It simultaneously utilises the 
principles of incandescence, of the arc, and of the extra spark. 
Among the candles and candle lamps of course Jablochkoft’s 
candle is the most prominent. It was invented in 1876, and 
has the special advantage that it entirely dispenses with any 
