302 Scientific Intelligence, [May, 



trees, often of great size, and with their lateral branches still 

 attached to them. These remains of an ancient forest extend to an 

 unknown distance into the sea. 



Article XIII. 

 SCIENTIFIC intelligknce; and notices op subjects 



CONNECTED WITH SCIENCE. 



I. Lectures. 



The Summer Courses of Lectures on the Theory and Practice of 

 Physic, by Dr. Roget, and of Materia Medica and Medical Juris- 

 prv;dence, by Dr. Harrison, will commence, as usual, in Wind- 

 mill-street, on the first week in May. The Lectures on Chemistry 

 will, in consequence of Dr. Davy's absence from town, be given 

 during the summer l)y Dr. Granville. 



Dr. Clutterbuck will begin his Summer Course of Lectures on the 

 Theory and Practice of Physic, Alateria Medica, and Chemistry, on 

 Friday, June 2, at ten o'clock in the morning, at his house, No. 1, 

 in tiie Crescent, New Bridge-street, Blackfriars, where further par- 

 ticulars may be had. 



II. Gas Lights. 



In answer to M., who puts some queries on the subject of gas 

 lights in tlie last number of the Annals of Philosophy, p. 313, I 

 have to observe that, in all my experiments on carbureted hydrogen 

 gas I never was able to produce an explosion by firing any mixture 

 of it whatever with common air. It merely burnt rapidly. Such a 

 rapid combustion on a large scale I am sensible would produce an 

 explosion. When mixed with oxygen gas, it will not fire unless it 

 bear a certain proportion to the oxygen gas. The oxygen gas must 

 amount at least to J 05 measures (supposing we take 100 measures 

 of carbureted hydrogen gas), and no explosion takes place wlienever 

 the oxygen amounts to 227 measures. From these facts, I infer 

 that whenever 1 1 parts of common air and one part of carbureted 

 hydrogen are n)ixed together, the mixture will explode when 

 kindled ; but if the carbureted hydrogen exceed -^th of the common 

 air, it will no longer be capable of exploding. All proportions 

 between -^th and -^th will explode. 



The gas produced by the distillation of pit-coal consists almost 

 entirely of carbureted hydrogen. Hence I conceive that the pre- 

 ceding observations apply to it correctly; of course coal gas, when 

 collected in reservoirs, never can explode unless it be mixed with at 

 least six times its bulk of common air. This I think never can 

 happen except from an unaccountable and culpable negligence of 

 tho&e who are employed. If the reservoii- is not air-tight, if it J3C 



