ON THE THEORIES OF ELEVATION AND EARTHQUAKES. 51 
the tbiekness of the shell should be least. The Inequality thus introduced, 
however, could never exceed a quantity of the same order of magnitude as 
^e solar nutotion, and for any but the most incousiderable thickness of the 
shdl would be cntiady inappreciable by observation. 
npi nf*?' ‘^-2 ““ evidence AS to the thick- 
supposing the earth constitutol as above assumed. 
Soettv /S°f appeared in the Transactions of the Royal 
boeiety (Part I. for mo), I resumed the investigation without the liiuita- 
thTlnTent/ft‘™?T^'? "1 assuming both the solid sliell and 
morTIll,? h .i^PierogeneHjuA n.c result showed that under this 
precession and nuUtion depended 
fael ot-f . i2 7®"” the eUipticiliesof the external and intern^ sur- 
laces ot ti e shell, and on its thickness, or on this latter quautitr alone, if we 
^ M “ fulicSon of the thickness, 
to hTp r T l *■« have done, thn solidity of tb^ 
shell to have resulted Irom its relrigcration. In a third memoir in Uie 
tTc thickn^2ff L"'^''T“‘^ memoir to determine the numerical vllue of 
nreceS Thp u .f to the present observed amount of 
A. i. f/tirhtesa of iht solid shell 
^ o^ie-yorirtA or oriefifth of the radim of its ezUrrusl 
dfe^Pof? this result, implies in itself some 
fiS^nrh^'r H «. ’vl^ich in fact must necessarily exist 
I have nn dn iV^ /'f ”” " calculation rests. At the same time 
oftheerusl-i**^ * -'f *!* T* upproxilimtion to the inininiuiii tliickncss 
ever ttelre 1 ‘ o'-’»fp«!Ce8eiou. It i. not, how 
lie mo« rV““‘ •"'‘hi* thiekDese wkiei. 1 regard aa 
tuSifnf . r ra' "'“‘'‘f e"' '■"■“»<>«. i» »«t 'Vlielter the 
tfmn 800 nr inon*^ eviiat ot the globe be somewliat uiorc or aoiacwhat leas 
he h asTof S “ !>» Of be oot very much le.a than 
(nr .T f-. Poial the problem affords US distinet 
to™;i Jo ‘•‘‘emonstra ed that if the thickness of tlio srdid shell were 
siblv thp «flm * earth’s radius, the precession would be sen- 
eSeitvT 1 ‘ ^ Iioraogoneous spheroid with its actual 
amSnt!^’ one-eighth part than the observed 
livShil^lr?'^ « inconsistent with the 
0 "“J “t^ers, that the solid crust of the globe 
floes n. t exceed tw'euty or thirty miles in thickness. 
tion to ut^inil J* reumrk the hearing of this result on the ques- 
liuencc on ih * before alluded, viz. whether high pressure has any in- 
the ° fnsion of solid substances. The result that 
elusion tliiit n crust U large, is in fact inconsistent with the con- 
the aiirfii/vo A* ^“^*00 i* the sumc alditfiTciit depths beneath 
> r IS unaflcctcd by high pressure, if we admit the existing tem- 
tenninate^ti!rfo£ **** *‘*l'P‘**®d If •»« lionndpd interiinlly by a de- 
intcriwl uibm «».' s '“***’* 1rftn%iiion from iht solidity of the shell to On.' Iluidify of the 
•he trojisitian mu {"‘"f**** “*"* whma« in any actual case like tlai of lUe earth 
tills end oilifr‘Ictcniiimitioii of tlio limits of the iinckrtainty in 
cate anDrn,im..<' *' of the accurucy of the various and often deli- 
entire solution ‘'"'oli'eil m die problem, I can only refer to the memoirs containing the 
B 2 
