868 



SCIENCE 



[N. S. Vol. XLIV. No. 1146 



nearly round, are usually yellowish to white 

 in color, and generally carry fossils of coral, 

 brachiopods, and bryozoans common to the 

 limestone. 



At many places between outcrops of the lime- 

 stone occur beds of limestone cobbles which 

 are more or less silicified and in all respects 

 identical with those found in the disinte- 

 grating limestone. Furthermore, upon noting 

 their elevations, these isolated beds of cobble 

 Btones are found to lie in the plane of the 

 limestone — never above it, and only scattered 

 or displaced cobble stones are found below the 

 plane. These facts point unmistakably to the 

 limestone as the source of the cobbles and bear 

 evidence of the former presence of the lime- 

 stone at all points where these beds occur. 



Wherever the Mississippian-Pennsylvanian 

 contact dips much below the plane of the Max- 

 ville limestone, little or no trace of the lime- 

 stone was found. Where the contact is not 

 far below this plane, silicified cobble stones 

 are often found in the base of the Coal Meas- 

 ure basal conglomerate which are identical 

 with the residual cobbles of the limestone. 

 Within the belt considered the contact some- 

 times falls 100 feet or more below the Max- 

 ville plane and all such places have been found 

 to be clearly defined valleys which trenched 

 the Mississippian surface. 



It is now known that the Maxville lime- 

 stone is found two thirds of the distance across 

 the state with strong probability of still fur- 

 ther extent formerly. 



The Berea sandstone, lying at or near the 

 base of the Mississippian system, is an ex- 

 cellent datum plane. Using it for this pur- 

 pose in the general direction of the Maxville 

 outcrop, it is found that the Berea-Maxville 

 interval increases northward. In Vinton 

 County, in the southern part of the state, the 

 interval between the top of the Berea and the 

 top of the Maxville is about 650 feet; at 

 Rushville, in the eastern Fairfield County, 

 about 800 feet; at New Castle, in Coshocton 

 County, about 840 feet; near Killbuck, in 

 southern Holmes County, about 870 feet; and 

 twenty miles north of the last point in central 

 Wayne County east of Wooster a thickness 



of 900 feet of shale and sandstone above the 

 Berea does not quite reach the Maxville hori- 

 zon. Northward from Wayne County the total 

 thickness of the Mississippian strata decreases 

 notably, due to greater erosion in late Missis- 

 sippian time. In northeastern Ohio the Penn- 

 sylvanian beds lie, commonly, only about three 

 to four hundred feet above the Berea, and in 

 the old Mississippian river valleys, so clearly 

 defined in this area, the Sharon conglomerate 

 sometimes lies but 100 feet above the Berea. 

 These thicknesses are clearly far below the 

 Maxville horizon. 



Central Wayne County is about fifty miles 

 from Cleveland and 150 from Portsmouth on 

 the Ohio River, the region of the southern 

 outcrops of the Maxville. If the plane of the 

 Maxville be projected northward to Cleveland 

 with the slowly increasing interval between it 

 and the Berea, the Maxville would lie about 

 1,050 feet above the Berea. 



In the light of these facts it is apparent that 

 the Maxville will not be found in northern 

 Ohio, and that outcrops may not be expected 

 beyond northern Holmes, or central Wayne 

 County. 



It will be noted further that these figures 

 reveal the interesting fact that the Missis- 

 sippian system thickens northward, although 

 thinnest in the north now as a result of erosion. 



Mount Union College G. F. Lamb 



A METHOD FOR MAINTAINING A CONSTANT 

 VOLUME OF NUTRIENT SOLUTIONS 



With plant experiments involving the use 

 of various nutrient solutions it is important 

 that there should be no undue loss of solution 

 due to evaporation or the taking up of the so- 

 lution by the plant, as it has been shown that 

 an increase in concentration due to a loss of 

 water by evaporation or transpiration may 

 seriously impair results. 



To save time in refilling the culture vessels 

 to a constant volume the following simple 

 method has been devised. It works automat- 

 ically and keeps the solution at a constant 

 level, and the only attention required is to 

 refill the reservoir when empty. 



A drawing will show the arrangement of the 

 device, which consists of a flask or bottle of 



