98 
POPULAR SCIENCE REVIEW. 
Madrepores of the Infra-Lias of South Wales. — In a paper read before the 
Geological Society, on November 21, Dr. P. Martin Duncan stated the fol- 
lowing conclusions : (1) That the fossiliferous beds of Sutton, Southemdown, 
Brocastle, and Eivenny, are important members of the series which intervenes 
between the Trias and the beds containing Ammonites Hucklandi , Gryphcea 
incurva , &c. and that which has been named the Infra-Lias. (2) That the 
Mollusca and certain well-known species of Madreporana, which are grouped 
together at Brocastle, have similar relations to each other in the Calcaire de 
Valogne , in the zone of Ammonites Moreanus of the Cote d’Or, and in the 
Gres de Luxembourg. (3) That the above-mentioned beds in Wales, consti- 
tuting a coralliferous horizon, are the equivalents of the upper beds of the 
French and Luxembourgian Infra-Lias. 
Age of the Chinese Coalfields. — It will possibly surprise some of our 
readers to learn that the greater part of the Chinese coalfield belongs to the 
Mesozoic period. This has been recently demonstrated in the American 
Journal of Science ; the author of the article having received several specimens 
of the Chinese coal-fossils, has been enabled to determine that all the carbo- 
niferous fossils are absent, and that most of the plants present are Podoza - 
mites and Pterozamites, which are essentially Cycads. 
MECHANICAL SCIENCE. 
II. M. S. “ Water witch P This vessel, which has recently been tried, has 
been built to ascertain the value of the new system of jet propulsion, intro- 
duced b T ; Mr. Buthven, to which we have before adverted in these pages. 
The experiment is upon so large and costly a scale, and in the hands of men 
so thoroughly competent to carry it out, that the value of the system will 
doubtless be thoroughly investigated. We take the following particulars of 
the vessel from Engineering , vol. ii. p. 315 (October 26), which contains the 
most accurate description which has yet appeared. The “Waterwitch” was 
designed by Mr. E. J. Peed, and has been built by the Thames Shipbuilding 
Company. Her tonnage is 778 tons measurement, length 162 feet, breadth 
32 feet, depth 13 feet 9 inches. She has a flat bottom, and is double-ended, 
each end being fitted with a rudder. She is armour-plated for a length of 
about 60 feet amidships, with 4|-inch plates on 10 inches of teak backing. The 
propelling machinery was constructed by Messrs. J. & W. Dudgeon, accor- 
ding to the plans of Mr. Buthven. It consists of a set of three cylinder 
condensing engines, driving a centrifugal pump, by which the water is sup- 
plied to the jets, which constitute the propelling apparatus. The revolving 
wheel of the centrifugal pump is 14 feet in external diameter, and it has 12 
arms or vanes curving upwards and outwards. From the wheel case the 
water is conducted through two copper pipes, which leave the case tan- 
gentially, and are led with a spiral curve to the jets at the side of the vessel. 
The arrangement for directing the jets either forwards or backwards consists 
of a large two way cock, placed at each side of the vessel just within the 
delivering nozzles, and by turning these cocks the water can be delivered 
