378 Proceedings of Societies. [May, 
brightness and reversal ; and during the late eclipse the two 
most refrangible rays of hydrogen were not detected from the 
same cause. 
Chemical Society, April 3. — Mr. G. Attwood read a paper 
“ On a Gold Nugget from South America.” In the State of 
Guayana, Venezuela, a large area of alluvial soil has lately been 
found to contain gold, and nuggets up to 25 ounces have been 
discovered within 3 feet of the surface. Numerous gold-bearing 
quartz veins are found in the neighbouring hills. Quite one-half 
of these nuggets are covered with a dark brown substance, re- 
sembling a silicate of iron. Such a nugget was treated with 
hydrochloric acid (its weight diminished, after treatment with 
HC 1 and NaO, from 3047 grains to 284-33 grains). The solu 
tion contained — Silica, 0-12 gr. ; ferric oxide, 8*88 ; lime, 0*15 ; 
magnesia, 0*08. The nugget was then treated with caustic soda, 
and again with HC 1 . The solution contained — Silica, 4-66 grs. ; 
ferric oxide, 460; lime, 0*21. During this process much gold 
in a finely divided state became detached, and after the treat- 
ment the nugget was partly covered with a coating of finely 
divided gold, of a dull colour. The nugget contained 94-54 per 
cent of gold. The gold from the quartz veins contains 87-9 per 
cent gold. From these experiments the author concludes that 
gold nuggets gradually increase in size, owing to the accumula 
tion of fresh particles of finely precipitated gold. Specimens of 
these nuggets showing the dark glazed coating were exhibited, 
including one weighing over 14 ounces. 
Institution of Civil Engineers, March 25. — Mr. Bateman, 
President, in the chair. The paper read was on “ The Elecftric 
Light applied to Lighthouse Illumination,” by Mr. J. N. 
Douglass, M. Inst. C.E. The author showed the progress of 
lighthouse luminaries from wood and coal fires to the intro- 
duction of tallow candles, fatty oils, mineral oils, coal gas, and 
eleClricity. In 1839 experiments were made by Faraday, for the 
Trinity House, at the Orford Low Lighthouse, with the Bude 
light, and, in 1862, at the South Foreland with the Drummond 
or limelight, but the results were not so satisfactory as to lead 
to their adoption. In 1857 experiments were tried at Blackwall 
with the elecftric light, produced by the first magneto-electric 
machine of Holmes ; and on the 8th of December, 1858, the 
elecftric light, obtained by Holmes’s second machine and a 
“ Duboscq ” lamp, was sh nvn on the sea for the first time from 
the South Foreland High Lighthouse. On the 1st of February, 
1862, the Trinity House exhibited the elecftric light permanently 
at Dungeness Lighthouse, by Holmes magneto-eleCtric machines 
and lamps. The works for the production of the light were 
described, and the first cost and maintenance given. The inten- 
sity of the elecftric luminary was about I2£ times that of the oil 
