SCIENCE. cooling lagst be attriljuted tlie principal motive force. The main criticism raised against it is its insufficiency, but George Darnin has shown that as a cause it can be mathematically sl~own to be able to procluce results at least of the same order as those observed. I n tllc speaker's estimation it is probably sufficient, altliougli the heat 12cliatecl is a very clifficnlt thiag to iucasnre in a reliable way. Our data are all from the continents, and they have not beell obtained in
... beell obtained in sufficient quantity. Tlle oceanic areas are necessarily nnobserrccl. 1 1 1 discussion Professor Kemp stated that attention had been naturally been drawn to tlie interior of tlle earth in the endea~or to explain, first of all, tlie contrasts of the continental elevations and the oceanic abysses, anc1 seconclly, the crumplings, folclings and faults-of mo~ultainous regions. Herscliel's esplalmtion, while rational and simple on the face of it, is inapplimble because i t is the area of sedimentation, subsidence and 'overloading ' tliat later on is uplic~aved in the mountains, and tliis apparent contracliction is tlle great difficulty. H e also rcfcrrecl to tlie measures of rigidity of the crust, to the remafiablc localizatioil of tlle yielding along narrow lines wllen it did come, and to its great effects and relatively short duration. H e asked Profcssor TTTooclwarcl also to touch on the slowing up of the revolution of tlie earth and tlie consequent rcadjustment of tlie spl~eroid to tlle loss of centrifugd force, an iclca aclvanced some years ago by TIT.B. Taylor. I n reply Profcssor Woodward admitted that the questions were old ancl very difficult ones, and that for tlle mountains lle had no explanation to advance. H e spoke of the mountainous protuberances as measures of tlie rigidity, and yet this must be qualified by the statement that according.ts isostasy ancl to recent pendulnm observations they appear to be somewhat lighter under the surface. As to the sloning up of rotation and loss of centrifugal force, tlie idea was an irnportant and valuable one, but i t clid not appear to be sufficient to account for the results. Professor Rees referred. to tlle recent observations on changes in latitude made under his direction, and to certain factors that entered into tllc calculations which would t,llron-light on tlle question. Professor Hallock brought 1111tlle recent results of experiments on tlie gyration of liquicls as bearing on the question and proving that a fluid set in rapid rotation continues to gyrate long after the enclosing ~e s s e l ceases. Thc curious results obt,ained a t the TITaterville arsenal in tlie great tcsting machine were also cited. The attempt was made to burst a cast iron cylinder by forcing into it, through a tlwee-sixteenth of an incli hole, paraffine and tallow. But it was found that both these substances became, uncler high pressures, more rigicl than steel and could not be driven tlirough the hole. Prof. Britton asked Prof. TVoodn-ard if the amount of heat r a d i a t d per ann~um could be quantitatively expressed, and in reply Prof. TIToodnrard said i t is computed from very meagre data to be enougll to melt a layer of ice 5 to 7 mm. thick over tlie earth's surface. The ellairman, Prof. R. P. XTllitfield, in closing the discussion called attention to the fact that tlie submarine crumpling and upheaval were not well knonv nor often taken into account, and yet they probably far exceed all that n-e see on the continents. Tlie ciiscnssion will be continued a t the meeting of the Scction, February 15.