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POPULAR SCIENCE REVIEW. 
often entirely tilled with boiling water containing various mineral salts in 
solution. In the course of time incrustations (sometimes to the thickness of 
several feet) are formed on each side of the fissures, composed chiefly of 
hydrated silver, but containing also oxides of iron and manganese, traces of 
copper, minute crystals of iron pyrites, &c. The author thinks that these 
phenomena tend to show that the Theory of Ascension, which teaches that 
veins are the result of deposits of mineral substances which have been intro- 
duced into fissures from below, is the most rational method in which to view 
this formation. For further corroboration he gives analyses of water issuing 
from lodes in some of the deeper Cornish mines which were found to hold 
mineral substances in solution. 
The KiUorkcm Fossils , co. Kilkenny , Ireland , have recently been explored 
by Professor Oswald Heer, who read a paper before the Geological Society 
[Jan. 10, 1872], On Cyclostigma , Lepidodendron, and Knorria from Kil- 
torkan. In this paper the author indicates the characters of certain fossils 
from the Yellow Sandstone from the South of Ireland, referred by him to 
the above genera, and mentioned in his paper a On the Carboniferous Flora 
of Bear Island,” read before the Society on Nov. 9, 1870 (see Q. J. G. S., 
vol. xxvii. p. 1). He distinguished as species Cyclostigma Kiltorkense , 
Haughton, C. minutum , Haught., Knorria acicularis, Gopp. var. Bailyana, 
and Lepidodendron Veltheimianum , Sternb. In the discussion on the paper 
Mr. Carruthers differed from Professor Heer as to his method of arriving at 
conclusions upon the fossils. 
A Geological Map of London is, we are informed, shortly to be published 
by the Geological Society. This will be a great boon to our metropolitan 
workers, and we trust it will soon be out, and that it will be well done. 
An Earthquake at Malaga is recorded in a letter which the Minister for 
Foreign Affairs laid before the French Academy at its sitting on February 
26, 1872. The shock occurred on January 28, at 3h. lm. in the afternoon. 
The undulating movement lasted from four to six seconds ; there were sub- 
terranean sounds like thunder some moments before. The shock took 
place from north to south. The weather was unusually cold, the birds were 
visibly affected, and uttered peculiar trembling notes. No mischief is re- 
corded as having taken place. 
MECHANICAL SCIENCE. 
JDiagrammagraphe. — In investigating the proportions to be given to slide- 
valves and gear, it is usual to employ various geometrical constructions, by 
which the action of the valve in opening and closing the steam ports is 
represented. In the case of valves worked by link motions, these diagrams, 
though extremely valuable, are in general only approximate representations 
of the action of the valve ; that is, in order to simplify them the influence 
of the obliquity of the eccentric rods and of the connecting rod is ignored. 
M. Pichault has invented a beautiful instrument, which he calls a diagram- 
magraphe, by which any given arrangement of link motion can be tempo- 
rarily put together, and a pencil moved in precisely the same manner as the 
actual valve would be moved with the proposed link motion. This pencil 
