416 Chronicles of Science. [July, 
machine, is now adapted to mining and tunnelling with advantage; 
and one of those machines is employed in an open quarry, doing its 
work well and with economy. The legislature of Massachusetts have 
asked General Haupt to take charge of the Hosaic Tunnel. 
Mr. Lowe’s boring-machine is reported on as doing good work in 
Australia. We have consequently three machines competing with 
each other, and proving their relative values under different cir- 
cumstances. We hope to see those machines employed ere long in 
our mines, to relieve the miners from the most trying part of their 
labour. 
10. MINERALOGY. 
Is it desirable that the mineralogist should cast aside all those long- 
established formulae by which he expresses the chemical composition 
of his mineral-species, and introduce in their stead a new set of 
formule, written in accordance with the advanced views of our 
modern chemists? Such is the question which Professor von 
Kobell discusses in a short but interesting paper “On Typical and 
Empirical Formule in Mineralogy.”* Typical formule, we need 
hardly say, are those in which certain compounds (such as hydro- 
chloric acid, water, and ammonia) are taken as general types, from 
which other bodies may be derived by replacing their constituents, 
according to definite laws, by other elements or by groups of 
elements called radicals. To illustrate the application of this type- 
theory to express the constitution of minerals, our author selects 
the double silicate of potash and alumina, called Jeucite. The com- 
position of this species we are accustomed to represent by the 
following formula : 
KO, Si O, + Al, O,, 3 Si O2. 
But behold the aspect which our formula assumes when written 
on the type-theory : 
It may be necessary to remind those of our readers who have 
not kept pace with the advance of modern chemistry, that such an 
expression simply means that the mineral in question may be 
regarded as formed on the water-type, and that the 24 atoms of 
* ‘Journal fiir praktische Chemie,’ 1868, p. 159. 
