On the Laws of the Distribution of Life and of Rocks. 405 
gulum ani distincte excavato, aliter directo ; venis omnibus fere 
velut in Taygetide. Caput oculis nudis; palpis elongatis, extror- 
sum paulum porrectis ; antennis tenuissimis, vix clavatis. 
Amphidecta piynerator, sp.nov. Pl. IX. fig. 11. 
Alee supra fuscee, area apicali anticarum et margine apicali postica- 
rum obscurioribus ; costa anticarum et angulo anali posticarum 
roseo-rubris: anticee costa basali nigro liturata; maculis tribus 
discalibus albidis triangulum formantibus: corpus fuscum. 
Ale subtus pallidiores: anticee minime violaceo tinctz ; apice fusces- 
cente; area apicali et costa nigro lituratis ; maculis velut supra, 
_ quartaque intermedia cuneata submarginali, albidis, plaga pur- 
pureo-fusca inclusis: postice albide roseo tinctee, omnino fusco 
striate; apice niveo; angulo anali ferruginoso ; lineis duabus 
_ mediis male definitis irregularibus; margine externo fuscescente ; 
punctis sex discalibus albis nigro punctatis, serie undata positis : 
corpus ochreo-cinereum. 
Exp. alar. unc. 2,%. 
Hab. Ega. Coll. Bates. 
Taken in the depths of the forest. Flight low and weak. 
Only a single specimen found. (Bates’s MS.) 
XLIX.—The Method of Geology ; being an Account of the intro- 
ductory part of a paper on “ The Laws which have determined 
the Distribution of Life and of Rocks,’ read before the Cam- 
bridge Philosophical Society, Nov. 12, 1866. By Harry G. 
Sexevey, F.G.S., of the Woodwardian Museum in the Univer- 
sity of Cambridge. 
In their distribution over the world, the materials of rocks 
which are accumulated under water, and the materials of 
organized bodies, obey the laws of physics. The forces that 
these laws relate to, in this subject, are:—in the first place, those 
inherent in the earth itself, such as gravity and attraction, on 
the one hand, and motion in the earth’s crust; and, secondly, 
those acting on the earth from without, such as the heat received 
from the sun, and attractive forces which determine the earth’s 
relations to the solar system. That is, everything is kept in its 
place by gravity, out of which it is moved by heat and the forms 
of energy into which heat is changed ; while the area over which 
these forces operate in a given way is changed by movements in 
the earth’s crust producing changes of land and water. 
2. The motion of matter visible on the land is for the most 
part due to the sun’s heat—hence being derived those distri- 
buting powers the winds and rain and rivers, in their various 
Ann. & Mag. N. Hist. Ser. 3. Vol. xx. 28 
