designs for the furnace might be safely employed; such, for instance, as winding the resistance wire on an asbestos-covered metal tube. Having at hand, however, an alundum tube of suitable size, we found it convenient to wind the wire directly upon this tube, and to hold the wire in place with alundum cement. The alundum tube has an inside diameter of 11⁄2 inches (38 mm.) and is 4 inches (114 mm.) long. The winding consists of 51 turns (12 to the inch) of No. 30 nichrome wire (diameter 0.010 inch, or 0.25 mm.), giving a total of approximately 24 feet (7.3 meters) of wire. Its resistance is about 160 ohms cold and 200 ohms hot, and the current is about 0.6 ampere. The furnace rests on a disk of heavy asbestos board and is jacketed with ordinary asbestos-magnesia pipe covering. The neck of the still is covered with loose asbestos fiber.

4

Preliminary treatment of the mercury. As here constructed this still is intended for the final distillation of mercury that has been previously treated to remove the gross impurities. This may be done (a) by the well-known process of Lothar Meyer' since modified by Hildebrand3 and by Desha, in which the mercury is allowed to pass in a fine stream through a long column of dilute nitric acid; (b) by making the mercury the anode in a nitric acid bath and electrolyzing;5 (c) by passing air through the slightly heated mercury; (d) most thoroughly of all, by the method of Hulett and Minchin, consisting in subjecting the mercury to a preliminary distillation during which a stream of air is bubbled through it. The first three methods have recently been combined and developed into an automatic process. Another very simple but surprisingly effective method of removing impurities, which is not generally known and which has been ascribed to Henry Leffman, is to shake up the con

2 MEYER, LOTHAR. Z. Anal. Ch. 2: 241. 1863.

3 HILDEBRAND, J. H. J. Am. Chem. Soc. 31: 933-935. 1909.

1907.

DESHA, L. J. Am. Chem. J. 41: 152. 1909.

WOLFF, F. A., and WATERS, C. E. Bull. Bur. Standards 3: 624-625; 4: 9-11.

CRAFTS, J. M.

7 HULETT, G. A.,

Bull. Soc. Chim. Paris 49: 856. 1888.

and MINCHIN, H. D. Phys. Rev. 21: 388-398. 1905. PATTEN, H. E., and MAINS, G. H. J. Ind. Eng. Chem. 9: 600-603. 1917.

taminated mercury with cane sugar. After such a treatment and a filtration through a pin hole the mercury comes out remarkably clean.

Unless the mercury has been partially purified in some manner the tube A may become clogged by the accumulation of foreign metals which concentrate in the tube as the mercury distils.

If a wet process of purification has been employed, it is best to dry the mercury by bubbling air through it for several hours before introducing it into the still.

After a distillation from this apparatus the mercury should be given a filtration through a pin hole in a filter paper in order to remove a slight film of oxide produced by the oxidation of metal impurities by the small amount of air remaining in the still. After such a distillation and filtration the mercury may be safely used in vacuum gages and in thermoregulators, and for other purposes requiring a reasonably pure product.

The yield of distilled mercury is about 400 cc. per twentyfour-hour day, when the still is operated with a vacuum of approximately 1 cm. of mercury.

PHYSIOLOGY.-Sensory fibers in the mesencephalic root of man

and the guinea pig. WILLIAM F. ALLEN, Department of Anatomy, University of Oregon Medical School, Portland, Oregon.

As a result of Marchi stained serial sections of the brain stems of a five year old girl and two guinea pigs, in which the left Vroots of the guinea pigs were previously severed behind the semilunar ganglion and the V-sensory root of the girl had been destroyed by a large glioma in the pons region, the following preliminary statement can be made: A number of sensory fibers arising from cells in the semilunar ganglion follow the ventral surface of the sensory root of the trigeminal nerve into the brain stem to pass dorsally between the V-motor and the V-sensory (substantia gelatinosa) nuclei to end in considerable numbers in the motor nucleus. Other fibers continue dorsad and cephalad in the V-mesencephalic root to terminate in the

locus coeruleus. Degenerated fibers were fairly abundant in the mesencephalic root as far cephalad as the point of crossing of the IV-nerve root. A few of these sensory fibers apparently continue farther cephalad in the mesencephalic root to end in the V-mesencephalic root nucleus lateral to the central gray mass above the IV and III nuclei. Additional experiments are in progress to determine the distribution of the nerve fibers arising from the V-mesencephalic nucleus and the locus coeruleus.

CONCHOLOGY.-The land mollusks of the genus Obba from the

islands of Bohol and Panglao, P. I. PAUL BARTSCH, U. S. National Museum.

The United States National Museum has recently received a lot of shells belonging to the genus Obba, collected by Gilbert S. Perez on the islands of Bohol and Panglao, which made a revision of the group necessary. This has resulted in the recognition of a number of new forms, brief critical diagnosis of which are presented herewith. A fuller account and figures of these will be published in a monograph on the Philippine members of the genus, which is in preparation.

Obba rota Perezi, n. subsp.

The present race differs from Obba rota rota Broderip, which is at home on the island of Siquijor, in being decidedly more elevated and in having the peripheral keel less upturned at the edge, and situated about half way between the base and summit, while in Obba rota rota it is at the anterior extremity of the upper third.

The type, Cat. No. 216983, U. S. N. M., comes from Bilar, Bohol, and measures: altitude, 10.2 mm.; greater diameter, 27.6 mm.; lesser diameter, 22 m.

Obba rota panglaoensis, n. subsp.

This race is much smaller and darker than Obba rota rota Broderip. It is elevated like Obba rota perezi B. and has the keel similarly situated, but the sculpture is rougher in the present race.

The type, Cat. No. 216984, U. S. N. M., comes from 'Panglao Panglao Island, and measures: altitude, 9.7 mm.; greater diameter, 23.5 mm.; lesser diameter, 18.7 mm.

1 Published by permission of the Secretary of the Smithsonian Institution.

Obba moricandi hernandezensis, n. subsp.

The present race is more elevated and narrower than typical Obba moricandi moricandi Sowerby which comes from Jacna, Bohol. The pronounced characteristic color bands of the spire in the typical form are completely absent and only a faint narrow light-brown thread encircles the base. Our specimens come from Garcia Hernandez, Bohol. The type, Cat. No. 216980, U. S. N. M., measures: altitude, 19.3 mm.; greater diameter, 33.2 mm.; lesser diameter, 25.2 mm.

Obba scrobiculata valenciensis, n. subsp.

The rought axial sculpture, characteristic of Obba scrobiculata scrobiculata Pfeiffer, is reduced to a minimum, while the color bands on the upper surface of the typical form are merely indicated by obsolete. lines in the present race. The upper surface is marked by broad, light and dark oblique axial zones, which lend it a watered-silk effect. A color band is present on the base.

The type, Cat. No. 216986, U. S. N. M., comes from Valencia, Bohol, and measures: altitude, 13 mm.; greater diameter, 29.3 mm.; lesser diameter, 23 mm.

ABSTRACTS

Authors of scientific papers are requested to see that abstracts, preferably prepared and signed by themselves, are forwarded promptly to the editors. Each of the scientific bureaus in Washington has a representative authorized to forward such material to this JOURNAL and abstracts of official publications should be transmitted through the representative of the bureau in which they originate. The abstracts should conform in length and general style to those appearing in this issue.

GEOLOGY.-Notes on the geology and iron ores of the Cuyuna district, Minnesota. E. C. HARDER and A. W. JOHNSTON. U. S. Geo

logical Survey Bulletin 660-A. Pp. 26, with maps, sections, and illustrations. 1917.

The Cuyuna iron-ore district is near the geographic center of Minnesota, about 90 miles west of Duluth and 55 miles southwest of the western part of the Mesabi district. In contrast with some of the other Lake Superior iron-ore districts, it is without marked topographic relief. It is mainly a region of low, irregular morainic hills interspersed with lakes and extensive swamps and marshes.

The productive part of the Cuyuna district is commonly divided into two ranges-the north range, including the part lying north of the Northern Pacific Railway, and the south range, including the belt lying south of the railway. The discovery of iron ore in the Cuyuna district was entirely due to the existence of abnormal magnetic attractions in the region.

The bedrock in the district and adjacent region is largely concealed by a mantle of glacial drift that varies in thickness from 15 feet to about 400 feet. No rock exposures are known in Crow Wing County, in which most of the district is situated. The rocks that have been found up to the present time in the district can all be grouped under three classes: (1) sedimentary and igneous metamorphosed rocks interlayered with each other in beds and lenses and usually having steep dips due to extensive folding, (2) igneous rocks intruded into the metamorphosed rocks subsequent to their metamorphism and deformation, and (3) younger rocks which lie horizontally on the eroded surfaces of the rocks of the other two classes. The age of the various rocks is not definitely known.