i879*] Proceedings of Societies. 379 
luminary. The cost per unit of light per hour was o* 1165c!. for 
the oil, and 0*i2g4d. for the eledtric light. Frequent falling off 
of the latter light occurred, and the oil light had occasionally to 
be substituted. Shortly afterwards the French lighthouse 
authorities established the eledtric light at Cape La Heve, with 
the magneto-eledtric machines of the Alliance Company of Paris. 
In 1867 Holmes further improved his machine and lamp. Two 
of these machines and lamps were exhibited by the Trinity 
House at the Paris Exhibition of 1867, with a dioptric apparatus 
of the third order. The Souter Point Lighthouse was lighted 
by electricity in January, 1871. The light was adapted to a 
dioptric apparatus of the third order. A lower light from the 
same luminary as the upper one was adopted here for the first 
time. The optical apparatus for both lights was designed by 
Mr. James T. Chance, M.A., Assoc. Inst. C.E. A “Holmes ” 
fog trumpet apparatus was also worked from the same engines 
as the eledtric light apparatus. The total cost of the works was 
£18,000. The cost of the eledtric luminary per candle per hour 
was o-056d., being rather less than half of the cost per unit at 
Dungeness. The maximum intensity of the beam from this 
apparatus was about 700,000 candles. The Trinity House next 
established the eledtric light at the South Foreland High and 
Low Lighthouses, in January, 1872. The apparatus for the pro- 
duction of the light consisted of two steam engines of 20 effec- 
tive horse-power, four Holmes’s improved magneto-eledtric 
machines and lamps, and two dioptric apparatuses of the third 
order for fixed white light. The cost of the additional works for 
these lights was £14,800. The intensity of the full power beam 
from the High Lighthouse was about 20 times that of the old 
first order dioptric oil light. The relative cost per unit of light 
was as 100 oil to 30-6 eledtric. In 1873 the Trinity House 
adopted, for the Lizard Lighthouses, Siemens’s dynamo-eledtric 
machine and lamp, and a siren fog signal. These were driven 
by three of Brown’s caloric engines, each of 10 effective horse- 
power. The cost of the additional works for these lights was 
£14,936, and the annual maintenance, including interest on first 
cost, amounted to £2,365 6s. 4d. against £1,016 7s. nd. for the 
oil lights. The intensity of the full power beam of each light 
was about 330,000 candles, being about 21 times the intensity 
of the oil light. The relative cost per unit of light was 100 oil 
to 14*04 eledtric. The successive improvements in the eledtric 
machines, and in the means of driving them, had reduced the 
cost of the eledtric light at the Lizard to one-ninth of that at 
Dungeness, and the quantity of light produced at the Lizard 
per pound of coke consumed was increased 20 times. The con- 
tinued growth seaward of the shingle point at Dungeness led to 
the removal, in 1876, of the original eledtric light apparatus, and 
the substitution of a low flashing oil light and siren fog signal 
for both lighthouses. The author furnished information received 
