HARDWICKE'S SCIENCE-GOSSIP. 



67 



it has been produced since the hardening and con- 

 traction of the rock — for there are hard rocks which 

 do not exhibit a trace of cleavage, although in other 

 respects the same both chemically and physically as 

 clay slate — by intense and long-continued mechani- 

 cal pressure acting at right angles to the cleavage 

 Professor Tyndall has shown that pressure, and 

 Mr. Wear Fox that electricity* can be made to 

 produce lamination precisely analogous to cleavage. 

 Magnetic currents may have helped the particles in 

 nature to assume this definite direction. The course 

 of the cleavage in N. Wales seems to lend probability 

 to this view ; it strikes N.E. and S.W., the former 

 direction of the magnetic currents in this globe, or at 

 right angles to the direction of the mighty pressure 

 forces which have acted from the N.W. and S.E. 

 The combined action of pressure and electricity should 

 be tried on a lump of clay, and it should be ascertained 

 whether mere pressure on such a mass be capable 

 of producing electrical currents at right angles to the 

 direction of the pressure force applied. Even sup- 

 posing that the particles were deposited in lines in 

 the first instance, would not subsequent contraction 

 speedily efface such an arrangement ? The mechanical 

 pressure theory is supported by the following general 

 facts taken from nature, and I fail to see that Mr. 

 Malet's view satisfactorily explains any one of them. 

 I. In South America cleavage is to be seen remark- 

 ably parallel over hundreds of square miles of area 

 (Darwin). 2. Where cleavage is distinct, stratifica- 

 tion is obliterated. 3. The fossils and nodules of 

 cleaved rocks are greatly contorted, such rocks ex- 

 hibit mighty folds, and quartz bands in them have been 

 squeezed to a serpentine form into a space one-fourth 

 their former length. 4. The strike of cleavage nins 

 in the same direction as the general lines of elevation. 

 5. Strata showing cleavage are often curved, while 

 the planes of cleavage are perfectly straight and 

 parallel, and cross the planes of stratification at all 

 angles. 6. The Silurian strata of Wales have been 

 violently contorted and cleaved, while the same for- 

 mation in Russia is perfectly horizontal, exhibiting no 

 trace of cleavage. 7. Cambrian conglomerates near 

 Llanberis are all placed with their longer axes in a 

 direction parallel to the planes of cleavage, and 

 make high angles with the planes of stratification. 

 (Ramsay.) I do not think it has been shown by ob- 

 servation or experiment that simple contraction — i.e., 

 contraction by drying — will produce cleavage. The 

 cracks seen in dried mud and slime deposits cross 

 each other at many angles, cutting up the mass into 

 rough prismatic masses, and they can only be com- 

 pared to the joints of sedimentary rocks. Some 

 geologists suppose that the lateral pressure which 

 produced cleavage was caused by the contraction of 

 the earth's crust through the radiation of its heat, but 



* For the method of producing lamination in clay by voltaic 

 action, see Report of Royal Polytechnic Soc, 1837, pp. 68, 69. 



this explanation is open to grave doubts. We can 

 only judge of unknown forces by the effects they have 

 produced. This force — although it may no longer be 

 in action — has left a language inscribed on the rocks, 

 in no hazy characters, by which it tells us of its 

 past reign, just as hieroglyphics point back to a 

 mighty dynasty long since overthrown ! — E. Halse, 

 A.R.S.M. 



A "Missing Link." — Professor Cope has just 

 described in the "American Naturalist" the occur- 

 rence of remains of an anthropomorphous Lemur. 

 Professor Cope has named it Anaptomorphns homnn- 

 ailiis. He says the genus is nearer the hypothetical 

 lemuroid ancestor of man than any yet discovered. 



Fossil Remains in the Hollows of Fossil 

 Trees. — Professor Dawson, the well-known Canadian 

 geologist, has communicated to the Royal Society 

 a most interesting account of some explorations in 

 the coal formation of Nova Scotia. A large number 

 of erect fossil trees, chiefly those huge extinct club- 

 mosses called Sigillaria, were found, measuring about 

 three feet in diameter. These trunks had evidently 

 been hollow before they were fossilised, for in their 

 interiors was a quantity of earthy and vegetable 

 matter, crowded with the bones of small reptiles, 

 land-snails, and millepedes. It is presumed that 

 these creatures must have sheltered themselves in the 

 cavities. Professor Dawson gives an account of 

 twelve species of batrachians whose bones were 

 obtained. About half of the fossil reptilian remains 

 are new to science ; and many of the fossil insects 

 are also beUeved to be new species. Fifteen hollow 

 trees were examined, and found to contain fossil 

 remains. 



NOTES AND QUERIES. 



Swallows' Nests.— In the parish of Hartley West- 

 pall, North Hants, there is a cottage situated in a 

 meadow, it is some fields distant from any other 

 dweUing. At one end of the cottage is a shed, used 

 as a wood-house ; on a nail in the wall was sus- 

 pended Mr. Gillett's hand-saw, and on the top or 

 end part of the handle a pair of swallows stuck their 

 nest. On the children communicating the fact to 

 their father, he with a commendable, an exceptional 

 regard for the feelings of his feathered friends, en- 

 jofned them not to molest the birds ; and as I was 

 then the master of the school which the boys attended, 

 but which I have since been compelled to leave 

 through the intrusive interference of a person, I also 

 gave them similar advice. When the bird had laid 

 her eggs I went to look at them. The saw was taken 

 off the' nail, and carefully held to prevent the eggs 

 from falling out. Having looked at the eggs I hung up 

 the saw again, and waited in the garden to watch the 

 movements of the birds. They flew round very near 

 the shed, but did not enter. One of the children then 

 told me, that as I had left the door open the birds 

 would not go in, as they liked to fly in over the top 

 of the door, where was a little opening. The young, 

 brood was reared ; but as I left the neighbourhood, 

 I have not heard whether or not a second hatching 



