ANNIVERSARY ADDRESS OF THE PRESIDENT. CX1X 
effects which we should expect from the causes to which we have 
before alluded. 
Mr. Hopkins, after referring to the distortions of organic remains 
in cleaved rocks, observed some years since by Professor John Phil- 
lips, and more recently by Mr. Sharpe, remarks, that ‘‘ these distor- 
tions of determinate organic forms indicate corresponding distortions 
in those elements of the mass in which they are respectively com- 
prised.” To the memoir of Mr. Hopkins, read before the Cambridge 
Philosophical Society, we must refer for the mathematical reasoning 
employed. In conclusion he points out that the shells, after being 
subjected to the pressure due to the weight of the superincumbent 
matter (and it may be here observed that the rocks cleaved, and 
thence termed slates, were originally clay, or at most silt beds), 
would be again exposed to pressure in common with the general 
mass, when the latter was folded into flexures and contortions so fre- 
quently observed in the cleaved districts composed of our older rocks. 
He observes, that none but small pressures or tensions would be called 
into action in the strike of the beds by their elevation into straight 
anticlinal ridges ; and that two of the directions of principal tension 
or pressure would be in a vertical plane perpendicular to the direc- 
tion of the anticlinal line and strike of the beds, with which the third 
axis of principal tension must coincide. ‘‘The axes of greatest and 
least tension,” he adds, “through any point will lie in a vertical 
plane perpendicular to the strike of the beds, and consequently the 
intersections of the planes of greatest tangential action with the 
planes of the beds will be horizontal lines. Through every point 
there will be two planes of maximum tangential action perpendicular 
to each other, and therefore, dipping one of them in the same direc- 
tion as the beds, and the other in exactly the opposite direction, the 
strike of all these planes being the same.” 
Mr. Hopkins further remarks, that if we recognise the probability 
of the influence of internal pressure, though not as a primary cause, 
yet as effective in determining the positions of the planes of cleavage, 
we must suppose that these planes must coincide more or less accu- 
rately, either with planes perpendicular to the directions of maximum 
pressure, or with those perpendicular to the direction of minimum 
pressure, or with the planes of greatest tangential action. He also 
points out, that on the last supposition the lme of strike of the lami- 
nation must coincide with that of the planes of stratification, and 
considers that observation corroborates this inference. With respect 
to the opmion that currents of electricity have produced cleavage la- 
mination, Mr. Hopkins remarks that such views, and those founded 
on the distortion of organic forms, are by no means to be considered 
as opposed to each other, but that on the contrary they may assist 
each other, and be mutually useful for arriving at a correct theory. 
Even this notice of some portion only of the progress made 
in Geology during the past year (for it would require a volume 
instead of an address, necessarily limited as this must be, to enter 
