Jan., 1904 .] Thickness of the Columbus Limestone. 
67 
previously be allowed to dry at least twelve hours. Furthermore, 
the dish should be heated slightly above the melting point of the 
beeswax before the wax is poured in, and then allowed to gradu- 
ally cool before an open- front gas stove, thus allowing the bottom 
layers of the wax to harden first. This prevents the separation of 
the wax from the side of the dish as well as the' formation of 
cracks on the surface. Trays such as described have been in use 
in the laboratory at Kenyon College for more than a year, and 
have been found practical in every respect. 
Kenyon College. 
THE THICKNESS OF THE COLUMBUS LIMESTONE. 
Robert F. Griggs. 
So far as is known there is no exposure of the total thickness 
of the Columbus limestone. On account of its lithological simil- 
arity to the Monroe limestone below, the two are not usually 
separated in well records so that exact determinations from this 
source have been hard to get.* In the fall of 1900, however, the 
city of Columbus, in connection with a proposed storage dam in 
the Scioto River, drilled several wells into the rock to test its 
ability to withstand hydraulic pressure. Most of these were at 
such high levels on the bank that they did not penetrate to the 
Monroe. Two, however. Nos. 9 and 10, were drilled from 
near the surface of the river and passed several feet below the 
base of the Columbus. No. lowas located on the west bank, 
which is steep at that point. It was thought that by taking the 
section of this well and that of the bank the whole thickness of 
the Columbus could be obtained. The well was not driven in the 
ordinar}' manner, where the rock is broken into bits by a heav}’ 
drill and so mixed that the precise determination of any level is 
impossible, but a solid core was taken out, which broke only at 
the bedding planes and weak places. This core, together with a 
very complete record, are preserved in the City Engineer’s office. 
It allows the determination of the line between the two forma- 
tions to a fraction of an inch and the measurements throughout 
are much more accurate in the boring than those of the bank, 
which were taken with a Locke level, and so not susceptible of 
great accurac}-. 
The rock in the bank above is mostly covered, but fortunately 
a small quarr}^ has been opened at the top of the hill which shows 
the top of the smooth la3’er. The quart}" does not extend up to 
'•'The well in the State House 3’ard at Columbus, as interpreted bj* Newberry, show.s a 
tliickness of 138 feet for the Corniferous. which includes both Columbus and Sandusky 
formations. The upper component is shown to have a thickness of about 30 feet by 
numerous exposures in Franklin and Delaware Counties. Deducting this leaves a thick- 
ness of loS feet for the Columbus. Unfortunately, however, the record of this well has 
been found to be unreliable in some particulars and so is of scant authority in this case. 
