TTebkuaky 28, 1908] 



SCIENCE 



351 



There are other features of the specimens 

 that will be described and illustrated in a 

 larger paper on Malaysian basket work in 

 preparation. I wish now to call attention to 

 a new variety of textile and to inquire con- 

 cerning the existence of other examples. 



0. T. Mason 

 U. S. National Museum, 

 January 30, 1908 



KOTE ON THE " LAFAYETTE BEDS " OF LOUISIANA 



Some very interesting facts are being 

 brought to light in southern Louisiana by the 

 large number of oil-wells put down since the 

 date of the famous Lucas gusher in 1901. 



In undisturbed beds near the coast we find 

 the Quaternary moUuscan fauna extending 

 •down to about 2,000 feet. The drill samples 

 show sands, clays and gravels, the latter of 

 typical Lafayette type to at least 1,500 feet. 

 Oyster reefs are encountered more or less 

 frequently, showing a sinking of several hun- 

 dred feet in comparatively late times. In the 

 Texas Galveston well, and in the regions 

 where underlying beds have been brought up 

 near the surface, as in the Jennings oil field, 

 the first pre-Quaternary fauna is Miocene in 

 appearance, not Pliocene. It has been cus- 

 tomary to regard the Lafayette as approxi- 

 mately Pliocene. But our well records seem 

 to indicate that the seaward continuation of 

 the gTavels in the central portion of Louisiana 

 as well as in those states to the east and west 

 are rather Quaternary than Pliocene, and that 

 the whole embayment region, perhaps, was 

 above sea-level in Pliocene times and was 

 heing eroded instead of being below sea level 

 and receiving hundreds of feet of coarse lit- 

 toral sediment. It would seem then, that 

 Hilgard's views as to the contemporaneousness 

 and interrelationship of the coarse " Orange 

 sands " in the south and the ice sheets in the 

 north may prove correct in spite of the fact 

 that certain " Lafayette " gravels are said to 

 lie beneath glacial till farther north. 



G. D. Harris 



radiation which produces part of the ioniza- 

 tion in closed vessels is not due to y rays from 

 radium in the ground itself. It seems quite 

 probable that the penetrating radiation must 

 be due to radioactive products in the air and 

 it is quite probable that the origin of these 

 products is in the ground as Elster and Geitel's 

 theory indicates. 



The first method is based upon the radium 

 content of the various rocks as analyzed by 

 Strutt and Eve. The highest value for the 

 radium content of sedimentary rocks was 

 found to be 2.92(10)"'^ grams of radium per 

 gram of rock. The mean value found by 

 Strutt for sedimentary rocks was 1.1(10)"" 

 grams and by Eve .8(10)""^ grams. The value 

 of the radium content varies greatly with the 

 locality, but for surface soils which are sub- 

 jected to all the various kinds of weather 

 changes the radium content is probably 

 smaller than that found above. For instance, 

 Strutt found a radium content for chalk at 

 the bottom of a cliff to be .39(10)""^ grams and 

 at the top of the same cliff .12(10)''^ grams. 



.9(10)'" grams per gram of rock will prob- 

 ably be in general a maximum value for 

 surface rocks. This quantity will be called 



Q. 



Eve (Phil. Mag., Sept., 1906) has deter- 

 mined E, the number of ions produced per 

 c.c. by the y rays in air from one gram of 

 radium bromide supposed concentrated at a 

 point and at a distance of 1 cm. The num- 

 ber of ions produced per c.c. at a point near 

 the surface bv a semi-spherical shell of ground 

 of radius r and thickness dr is 

 2nrilr6KQ _^,, 



where 8 is the density (about 2.7) and \ is 

 the coefficient of absorption for the ground 

 (say .09). The factor .6 comes in since K is 

 given for radium bromide and Q for pure 

 radium; E is 3.1(10)°. The total number of 

 ions produced per c.c. per second by the 

 ground would be 



SPECIAL ARTICLES 



THE PENETRATING RADIATION 



In the present article three distinct methods 

 will be given to show that the penetrating 



I 



2nr^KQt1r _^,. 



This value comes out about .8 ion per c.c. 

 per second as a probable maximum amount. 



