158 Intelligence and Miscellaneous Articles. 



merits and flakes. The specimens of these exhibited were found by 

 the author between 1880 and 1885, and they establish the existence 

 of Drift-gravels about a mile south of Hayes Common. Some of 

 the implements have lost their pointed ends and bear other indica- 

 tions of use, many are smoothed and rounded by Drift -wear, but a 

 few are entirely unworn, while some, particularly the larger ex- 

 amples, are bruised and crushed by such influences as the plough- 

 share and waggon-wheels. Most of the implements have a superficial 

 colouring, varjing from a pale straw-tint to a rich ochreous-brown. 

 ' The association of much-worn implements, unworn implements, 

 and flakes, cores, and waste-chips, in the same bed of Drift-gravel 

 points to the fact that we have here a collection of material which 

 was brought from a great variety of places, and has undergone a 

 great variety of conditions and changes.' 



3. ' On the Occurrence in British Carboniferous Rocks of the 

 Devonian Genus Pa^c&oneilo, with a Description of a New Species.' 

 Bv Dr. Wheelton Hind, B.S., F.R.C.S., F.G.S. 



X. Intelligence and Miscellaneous Articles. 



ON KERR'S PHENOMENON. BY MM. ABRAHAM AND LEMOINE. 



I IQUTD dielectrics, sulphide of carbon for example, become bire- 

 fringent when placed between the armatures of a condenser. 

 The liquid is equivalent to a crystal whose axis is normal to the 

 faces of the condenser. It is shown by passing between the plates 

 a luminous beam polarized at 45° to the axis. A rdcol analyser 

 cannot extinguish it. 



When the electric field is done away with the birefringence dies 

 out during an inappreciable space of time. M. Blondiot has shown, 

 by a method founded on the use of a revolving mirror, that the 

 optical phenomenon does not exist more than ~^- Q second after the 

 removal of the electric field. The authors have been able to shorten 

 this interval. 



The condenser K is charged by connecting it with the poles P 

 of a high-voltage transformer. It is discharged suddenly in the 

 spark E, which is divided by an air-blast. If the amount of 

 birefringence during this discharge is measured, it should show 

 that this birefringence disappears during a very short time. 

 MM. Abraham and Lemoine have proved that it diminishes to 

 half in , AAA L A ^ second, and that it is no longer measurable in a 



400,000,000 ' ° 



little over j^^oo secon(L 



The measurement of the birefringence is made by employing the 

 discharge-spark E as source of light; it is very luminous and of 

 very short duration. The elliptic light which comes from the 

 condenser K is analysed by the so-called photometric method ; it 

 traverses the double-image prism B and an analysing nicol N 2 . The 



