and adjacent decomposed diabase. It especially is found in the veins in connection with the tetradymite, bits of decomposed diabase, and in the cavernous portions, but was not seen in the compact quartz of the vein itself. The tetradymite is in irregular grains and masses, showing a brilliant metallic lustre and a well-marked basal cleavage. This locality is worked for the gold, and was visited by the writer in December last.

A microscopic study of the Iron Ore of Iron Mine Hill, Cumberland, Rhode Island. By Dr. M. E. WADSWORTH, assistant in Lithology, Museum of Comparative Zoology. This ore has long been known and used in connection with other ores in the manufacture of iron. It was worked as early as 1703, and the cannon used in the celebrated Louisburg expedition of 1745 were cast, in part at least, from the iron thus obtained. It was extensively employed in the manufacture of charcoal iron in Massachusetts as late as 1834, and in 1869 was largely shipped to Pennsylvania to mix with other ores.

It does not appear that its true nature has ever been suspected, although numerous chemical analyses have been made of it; and it has been studied by Dr. Charles T. Jackson, Prof. Robert H. Thurston, and others.

A microscopic examination made by the writer showed that it was composed of magnetic iron and olivine. The magnetite forms irregular, more or less connected masses, making a sort of sponge-like structure. The rounded and irregular cavities and the interspaces between the magnetite masses are filled with the fissured olivine grains. It is found that, while the structure remains the same, the olivine has been altered to serpentine throughout a large portion of the rock. This iron ore is thus seen not to be an ore in the common acceptance of that term, but a rock which contains sufficient magnetite to allow of its being worked. It is a peridotite, and is closely related to the celebrated Taberg (Sweden) magnetic iron ore, worked for over three hundred years. This was studied microscopically by A. Sjören in 1876, and called by him " magnetite olivinite." Triclinic feldspar crystals, giving a porphyritic structure to the rock, are locally found on one side of the hill formed by this peridotite. The structure and mineral composition of the rock indicate an eruptive origin for it, since such has been the case with all similar terrestrial rocks whose history has been carefully worked out. Such rocks as this and others of the peridotites are the nearest allies to the meteoric stones that are known, and, as has long been suggested, give us the best clue that we have to the interior structure of the earth.

This may be pointed out as one of the cases in which microscopical lithology bears upon the practical side of life, since the iron-master who desires to use this rock can now for the first time understandingly grapple with the metallurgical problems it presents; whether he desires to use the rock as a whole, or only the concentrated magnetite.

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The Mouth-parts of the Larva of Dytiscus. By EDWARD BURGESS, Instructor in Entomology. The larva of Dytiscus, popularly known as the "water-tiger," is not mouthless, as heretofore described, but, on the contrary, has a mouth of unusual width. The lips are closely locked together by a dove-tail fastening, thus concealing the mouth-opening. Although it seems as if the insect could open or unlock its mouth, still the juices of its prey are sucked through the mandibular canal, as noted by

earlier authors, although not in the manner supposed by them.

The canal in question runs from tip to near the base of the mandible, as noted by Westwood, but does not enter the head. When the mandibles are brought together, however, the basal opening is brought within the corners of the mouth, and the sucking pharynx (with which this insect is also provided) then enables the insect to suck the juices of its prey through the mandibles into the mouth. Meinert has recently stated that the mouth-opening exists, but failed to see its dove-tail closure, or the modus operandi of suction.

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- White-ants in the American tertiaries. By SAMUEL H. SCUDDER. In the extensive collections of fossils made at Florissant, Col., six species of termites have been found, represented by twenty-six specimens, all but one of which are winged. This one is a worker, and, with a single exception from amber, is the only known instance of the occurrence of either worker or soldier white ant in a fossil state. The six species belong to three different genera; four species (of two genera) pertaining to the section with branched and two to that with unbranched scapular vein. This is the same proportion as holds with the sixteen species found in the European tertiaries, where eleven belong to the first, five to the second section. Of the modern types, on the contrary, only thirty-five per cent belong to the first, sixtyfive per cent to the second section. All the carboniferous, and perhaps also all the mesozoic, Termitina belong to the first section.

Three of the species belong to a distinct genus, apparently peculiar to America, but possibly including some from the European tertiaries; another is referred doubtfully to Hodotermes, which has furnished fossil species from several localities in Europe, as well as among living forms; while the other two probably belong to Eutermes, and are allied to species from Radoboj, placed, with many modern types, in this group. Calotermes, which has furnished species from amber and the Rhenish basin; Termopsis, which has more fossil (amber) species than recent; and Termes proper, which is represented at Oeningen and Radoboj, as well as in amber and on the Rhine, all seem to be wanting at Florissant. The composition of the tertiary white-ant fauna of Florissant, therefore, differs considerably from that of any locality in Europe, but it most nearly resembles that of Radoboj in Croatia, where a like number of species has been found. No white ants are yet known from any other tertiary deposits in America.

White ants are essentially a tropical family, only one or two out of over eighty known species occurring north of latitude 40°. In North America only three have been recorded north of the borders of the Gulf of Mexico, excepting on the Pacific coast, where one or two more extend as far as San Francisco. Two species, both belonging to the second section, are found in the valleys below Florissant in 39° north latitude. Florissant itself is situated 2,500 metres above the sea, and the presence of so considerable a number and variety of white ants embedded in its shales is indicative of a much warmer climate at the time of their entombment than the locality now enjoys.

-A Paper on the Propagation of Magnetic Waves in Soft Iron. By HAROLD WHITING.

This paper was presented to the American Academy through Prof. TROWBRIDGE, Feb. 14, 1881, and is printed in the Academy's Proceedings. p. 322.