1875.1 Notices of Books. 375 
of valuable minerals being thrown away from ignorance of their 
nature, he continues—“ But it is only the mistakes which have 
been discovered that can be known: it is very probable that the 
majority of such mistakes are never found out at all. The only 
safeguard for the future is in the multiplication of mineralogical 
observers.” 
Prodromus of the Paleontology of Victoria, or Figures and 
Descriptions of Victorian Organic Remains. Decade I. 
By F. McCoy. Melbourne: John Ferres. 
Tuis work is the first number of an Appendix to the Geological 
Survey of Victoria. It is to contain figures and descriptions of 
the more charactefistic fossils of each formation. The present 
number contains two plates of species of Graptolites, from which 
the Author determined the Lower Silurian geological age of the 
slates containing gold reefs. Then follow plates of the extinct 
fossil wombats from the gold cement of Dunolly, which afforded 
proof that the Victorian gold-drifts, like those of Russia, are of 
the age of the mamnimaliferous crag of the English Pliocene 
Tertiary age. Next are two plates of volutes, representing the 
Volutilites of the Barton clay formation of Hampshire ; a plate 
of the Cycadeous plants characteristic of the oolitic coal-fields of 
India, China, Virginia, &c. Finally come plates of character- 
istic genera of fossil vegetation of the palzozoic coal formation, 
and of fossil star-fishes from the Upper Silurian rocks. 
The work, when complete, will be a most valuable addition to 
palzontological literature. 
A Handbook of Hydrometry. By James Boppry KEENE: 
London: Pitman. 
In this little treatise the Author gives an account of the con- 
struction and uses of the various instruments employed for 
taking the specific gravities of liquids. With hydrometers the 
same confusion prevails as with weights and measures. Almost 
every country has its distinct scale; and to convert the indications 
of one of these into another is not always an easy matter. 
Throughout the civilised world water has, indeed, been adopted 
as the starting-point, but it is not everywhere taken at the same 
temperature. ‘In France water is taken as unity at its greatest 
density, which is 4°1° C. or 39°4° F. This point has the advan- 
tage of presenting no appreciable change of density within.a 
slight range above or below it: It is, however, so far below the 
average temperature of the year as mostly to require artificial 
cooling, and to be liable to rapid change of temperature.” 
VOL. V. (N.S.) 35 
