NOTE ON THE GLACIAL DRIFT IN ST. LOUIS.

H. A. WHEELER, E. M.

(Read in somewhat less extended form at the meeting of the Academy of Science, April 1st, 1892.)

In driving a tunnel under West Pine street, in the western-central part of St. Louis, for a sewer, the blue glacial clay or "till" was found for a distance of about 2,000 feet. A shaft at the junction of Taylor avenue and Pine street, which was about the middle of the till formation, disclosed a thickness of 12 feet. The blue-clay carried gravel and boulders as usual, and though none of the latter exceeded a foot in diameter, they were largely made up of distant-carried material, or crystalline rocks from the North like granite, mica-schist, white-quartzite, besides white saccharoidal sandstone, chert and limestone. It rested on the St. Louis Limestone (subcarboniferous), and was overlaid by 10 to 15 feet of the non-pebble bearing loess, or the unstratified, columnar jointed, brown, homogeneous sandy-clay formation (the "brick-clay "). The till feathered out on the west side of Euclid avenue, and was not again encountered in the westerly extension of the sewer.

From the limited width of the till, as the sewer-section was on about an east and west line, and the comparative thinness, not exceeding 12 feet, it seems to be a local tongue or extension of an ice-stream beyond the main body of the southern limit of the great ice-sheet. The nearest recognized development of the till is at the Chain of Rocks region, or ten to fifteen miles north, where heavy sheets of mixed gray and brown clays and sands, carrying pebbles and boulders of foreign rocks, occur in the tongue of land between the Mississippi and Missouri rivers. In this region the till attains a thickness of over thirty feet, and contains, as erratics, red pegmatite, granitite, red and gray granite, diorite, dolerite,

quartz porphyry (like the Keweenaw Point series), porphyrite, red quartzite, quartz geodes (Keokuk), white "sugary sandstone (Saccharoidal), besides abundant cherts from the immediate neighborhood. But no blue-clay has been observed there, and the Pine street sheet is the only occurrence of blue till known to the writer in Missouri that is south of the Missouri river, which lies 12 miles north.

A thin layer of gravel bearing loess (?) is usually found at the base of the true loess throughout St. Louis County, as far as 10 to 15 miles south of Pine street, and while most of the pebbles are local cherts, they occasionally include distant material like granites, etc. This gravel bearing bed is always thin, ranging from to 2 feet in thickness and is similar in character to the transition bed that is found about the Chain of Rocks region between the typical loess and the typical drift, or has the general character of the loess plus more or less gravel, though usually only a little gravel is present. It totally lacks the character of the true till, and cannot be regarded as an ice-sheet deposit. This Pine street occurrence of till is therefore the most southern known extension of the ice-sheet in St. Louis County, though the Illinois lobe advanced considerably further south, according to the studies of Leverett, Salisbury, Chamberlain, and others.

I am indebted to Mr. Robt. E. McMath, the former sewer-commissioner, for calling my attention to the Pine street blue-clay.

Issued February 21st, 1895.

NOTE ON AN OCCURRENCE OF BLENDE IN

LIGNITE.

H. A. WHEELER, E. M.

(Read at the meeting of Academy of Science, of November 19, 1894.)

In excavating for the foundations of the new high-service pumping-station at Baden, in North St. Louis, fragments of blende-bearing lignite were found in the "Ferruginous Sandstone" at a depth of about 25 feet. The pit is in the riverbottom at the base of the bluffs that mark the western edge of the valley of the Mississippi river, being about half a mile west of the present river-bank, and furnishes the following

St.Louis Limestone-average depth, 32′ > Sub-Carboniferous.

The excavation stopped at the limestone, on which the coalmeasures rested unconformably.

The sandstone in which the fragments of lignite occurred was coarse-grained, porous, cross-bedded, light-gray to darkdrab in color, and rich in lignitic streaks with occasional fragments several inches in thickness. Some of these fragments of lignite or brown-coal are full of longitudinal and transverse desiccation cracks, which are completely filled with

crystalline mixture of sphalerite or zinc-blende, calcite and pyrite. The blende decidedly predominates, forming thin seams to inch in thickness through the lignite, and is light to dark brown in color, has a perfect cleavage, and the usual resinous fracture. Calcite, of the white, crystalline

original system.

Here, however, we meet with complications. The electrified surface must break up into separate closed sheets, surrounding the various bodies of the system. Some of these surfaces may surround bodies which were originally positively charged, and others bodies which were negatively charged. The charge on the collapsing surface is, however, all of one sign. It is like a case where equal terms of unlike sign in an equation have destroyed each other during an operation. They will not replace themselves when the operation is sought to be reversed. If, however, we intelligently restore the charges to the separating sheets of the collapsing surface until we have reproduced the original electrification, then the energy which we have applied to the surface is the energy of the system. But all of this leaves untouched the question concerning the nature of the force against which we have been working. There is reason to believe that it is not mutual repulsions between the elements of the electrification. There is reason to believe that it is a reaction between the electrification and a stressed condition which is impressed upon each element of the medium, as soon as it becomes external to the surface.

The electrical system is in fact produced by forcing the charges upon the surfaces of the cavities in the medium which the bodies occupy, and the condition of stress is propagated outwards and is maintained in some manner at present unknown.

It is evident that the evaluation of the volume integrals involved in determining perviance, resolves itself into a determination of electrostatic capacity. This is capable of direct determination by discharges through a ballistic galvanometer. As the same integrals are involved in determining magnetic permeauce, it seems feasible to apply this method to a study of many cases of leakage from magnetic circuits. It would only be necessary to construct wooden or other models having conducting surfaces, and having the forms to be investigated.

For resistance to electric induction or the reciprocal of