HOW TO OBSERVE—GEOLOGY.

THIS is the first volume of a new undertaking, of an ingenious de- sign and highly useful aim. The object of Mr .DE LA BECHE is to teach persons who neither possess profound acquirements nor regu- lar scientific knowledge, to observe such facts as fall in their way : his purpose is to afford to every active individual a constant source of rational interest and amusement, whilst he sends out in all di- rections numerous collectors of the statistics of science. The plan, when completed, will embrace many subjects,—Natural History, Agriculture, and so forth : the present volume is devoted to Geo- logy; and should be in the hands of every one who has acquired the merestelements of that difficult pursuit, or who has the means of acquiring them. With a knowledge of the various species of "racks- (which technical term includes soils), and our author s directions, the purchaser will never be at a loss fur employment whilst he is on the earth. If he wanders along the beach, he may observe the effects which the sea has produced or is producing oil the cliffs, and endeavour to account tor them, from the nature of the rocks, the character of the sea, the defence offered by the beach, and the prevailing winds. Should he stroll by a river, there are the depositions to observe; does he travel through a country, there are the character of its rocks, their extent, and super-position; and —not to mention such matters as organic remains, the efiisete of volcanoes, earthquakes, or (more universal still) those of various deluges--there are the fields by which lie passes, the roads over which he is conveyed, and the pits and quarries by the road-side. Let us, by way of specimen of the style and subject, take a couple of extracts from two of the last-natued points; not with a view of showing " How to Observe,- but to what practical uses the observation may be turned.

Roors.

That the exrense of constt acting a new road, or of maintaining an old one

in good order, greatly depends upon the kind of ground under it, upon the faci- lity with which proper stone may be obtained for it, and opal the stability et the vatious rails which it may be tonna necessary to make in the rocks, is well known. It is not, however, so well known that these circumstances depend upon the geological structure of a country, and that a knowledge of this struc- ture would enable those who possessed it to determine whether. one line ut new road would be more costly than another ; whether, when it becomes a question to patch up an old line of road or construct a new one, the one or the other will be ultimately found least expensive; and that some kinds of stone should

Ire employed upon roads in preference to others, when several kinds can be readily obtained. The aunts of money annually thrown away in this country (tutu a want of due attention to the latter citcutruitance, must, coneetively, be very considerable. We have seen instances in which stone was brought several miles for new toads, when a better material was close at hand. It might be true that no quarrie.i were opened upon the better material ; but any person with a little geological knowledge would point out the proper places to do so, Roads generally are planned with regard to little el-e than levels and dis- tant...5; and if there be a small advantage in this respect between two lines in 1.etuur of one, that line will be selected, though often a fair amount of geological hilowleiho. would lie sufficient to show that the expense, nut only of burning, bat also of keeping up this road, trill be far greater than for the other. Good :ire in this lesio.et highly v•ilti..Ide, at they enable those who

have ai ipiat seta o.ts coin: coed w ith toads to see at some the kind of t. rhs over v Etch a 1q4,1,11 lino of road is into n.1:41 to pass. They also point out the proxiaiity of locks which may atItird good mann tills for stoning, either Lew or old loads.

soils.

It weill.1 b, difficult to find an iiittllig••tit fit ther, in a district where rocks of

! u■iittfalogh.:1 characters ticenr, who heels nut. to a certain extent, home th at lb, valne of each s:.il respect it thy depends upon the kind 'eh beneath it. lie may nut 1.110W, alai sedicely ever dots, why this

•••:-. I but the fact extt:Lat to Now, it is precisely a know- - . v.1,y %%1.4.1, cual;!,s a geolog:st,acquaititell with the mine- - • i o.La A:ten r.,41: in it .lash ici, to state that the soil formed

. •l tile .:-tab's, is I■cr s:appolt cue hi: it of cultivation 1:; -oo.e cases, the :1i particular itiodt of cultiva-

rim, which t limeath them ; the agricul- . hort..! trout cN twit, ;tea dirt the two .oils above the-e lacks will 1...: ....Tr.!! the satoe cultivation with cu-.sal advantage. The coninion country kto heavy, light, cold, and tile lilt, depends upon the kind of ii-elss beneath Own:.

Natural ,mil, are merely ducontio..1.41 pits of the stilieent rock. mixed with the eseeittistest poetess it vteetaltet substances which have gustn or fallen upon it. and with a proportion of animal substances detived front the drippings of Cle::..1.:CS 111.1VC it'll 11111.11 the vegetation, from dead insects and worms which once the surface. and bolo the decomposition of animals that have !lei it the tool, and which have toot altogether removed by those and i;:suld,, that art lit natiar.dsaarengers.

The pt:' Inatiency it natural soil, derenil, upon the relative positions they oc- cupy kseeli a. whether they are fortiori on the steep slopes ut hills or on level ;dams I; tat ii the porous or impervious character of the supporting Wray be

ri titer (w hence the 4"iilicitlty of facility with whicla the b•

vt.eh:ch ;twat: upon the cli.utc generally of the locality, wore p.tHciihnly d• the goantity I f which may fall in a given thee ; and upon the kind and antennt 1:t vcgetation upon them, by which they are 11111te Or less protected from winoval accoldihi g. to circumstances. Although stone plants glow without having their roots plunged in the soil,