667 
a Theory of the Earth . 
of things apparently the most common, when an exact 
determination of their nature may he interesting to theory. 
People may thus employ, with advantage, the means of 
confirming or rectifying their first observations, and of 
making profound researches and comparisons impossible 
to be made on the spot*. 
CHAP. XXIII. 
Instruments neccessary for the Geological Traveller . 
1. THE most necessary instrument is the miner’s ham- 
mer. It will be requisite to have two, of different sizes : 
one small, to break small fragments of rolled pebbles, by 
holding them in the left hand while you strike with the 
right. Its weight, including the handle, ought to be 
about ten ounces. The other must be larger, to detach 
fragments of rock, and to break large pebbles : its weight 
ought to be quadruple that of the small one. When I 
travel on horseback, I have these two hammers suspend- 
ed from the bow of my saddle. 
i. A. Two stone-cutter’s chisels: one small, of from 
* We think it our duty to subjoin here some advice to travellers in regard to 
the questions which they may ask in the different towns. 
Whence do they procure the materials proper for building’ ; such as lime, plas- 
ter, tiles, slate, stones of different kinds, and sand ? Do they burn turf or coal ; 
and where are they found ? Where do they procure their potter’s clay, fuller’s 
earth, the clay used for refining sugar, their whetstones and millstones ? To ob- 
serve with what the streets are paved; of what stones the steps of stairs are 
formed ; marks for boundaries, &c. ; and to learn from what place they are 
brought. To ascertain whether wells or the foundation of houses are dug ; and 
whether there are in the neighbourhood any ravines or precipices. These ques- 
tions will serve to facilitate the means of observing the nature of the ground, by 
pointing out the natural or artificial excavations that may exist in the neigh- 
bourhood, or which ought to be visited. For the same reason it is proper to 
examine the shores of rivers. It will be of use also to take a general view of the 
country from the tops of towers and of the highest steeples. It will be of some 
importance also to enquire, in the country, whether the inhabitants make use of 
lime, marl, plaster, coal, earth, or turf-ashes, for manuring their land ; and from 
what places these substances are procured. Til. 
