192 
THE GEOLOC+IST. 
tlio limestone of Analogues; tbe " clioin batard " of Lyoii ; the " foie de 
veau" of Bour^o^rne ; the Sinemurieu in part of D'Orbignv ; the " qua- 
trieme etage " of the Lias of D'Archiac ; the upper dolomite of Lombardy, 
etc. In the tabnlar vicv which the author gives, the JEtage InfraUasien 
is placed below the zone of Ammonites BucHandi, and is formed in the 
follo\^ ing manner : — 
1. Zone of A mmonites angulatus. 
2. Zone of Ammonites planorhis. 
3. Zone of Terehratula gregaria. 
4. Zone of BactryUium, reposing on 
THE KEUPER. 
Henceforth, if the author's vievrs are correct, these Avicula contorta beds 
Avould serve as the lower limit of the Jurass'c formation, and will form a 
datum line of great importance in studying the geology of the Alps. The 
Essay appears to be an extract from the excellent memoir by the Abbe, 
" The Palseontology of Lombardy." 
M. Morlot has given an account, in the ' Indicateur de Suisse,' of the 
finding of a part of a nodule of pyrites amongst the remains of the lake- 
dwellings of the Stone-age at Eobenhausen by M. Messikommer, which 
was furrowed by striking it against some hard substance, probably for the 
purpose of obtaining fire. Many fragments of pyrites have previously been 
found at the same place and at Wangen. Another specimen, as large 
as the first, and evidently used for the same purpose, has recently also 
been found by M. Engelhardt. amongst a great number of different 
antiquities, dating from the earliest ages to our own era, in a peat-bed at 
Sonder Brarup, in Denmark. 
XOTES AXD QUERIES. 
Cutting Diamonds. — There still seem to be, in the minds of most per- 
sons, some wrong notions relative to the manner of cutting diamonds, and 
especially this is the case in London. Although several notices and de- 
scriptions of diamonds have appeared in various serials and magazines of 
late, none of them describe the process of cutting, except in such a vague 
and unintelligible manner as to impress upon the minds of readers a simi- 
larit}^ of the method of cutting, to that of other stones. The principle, it 
is true, is somewhat the same, but the operation is distinctly different. It 
is also generally stated, that the workmen have such a very perfect know- 
ledge of the crystallography ot the diamond as to enable them to cleave 
it very readily. The fact is they know nothing whatever of crystallogra- 
phy, — at least as a rule, — and only cleave the crystals by experience. As 
to wh}^ a diamond should cleave in a certain direction, the}" cannot tell, 
nor could they explain w hy they strike it on one particular spot in order 
to do so. It is also generally stated that diamonds are cut on the pr n- 
ciple of " diamond cut diamond," two crystals being rubbed together till 
a facet is produced. They are certainly rubbed together to get them a 
little into shape ; but how ? If the reader rub two crystals of diamond 
together, he will find that he hardly makes an impression on either ; but 
if the stones are inserted in metal and attached to a holder, and these held 
in the hands, which are rested on a bench, the thumbs towards each other, 
then it will be found that the mechanical power or leverage obtained is 
very great, even sufficient to crumble and break such hard material as 
