3. What mollusk has a distinct head, and swims by fins attached to the side of the neck?
This is the Gymnosomata (Greek, “naked-bodied”), an order of pteropodous mollusks, destitute of shell. They constitute one family, the Cliidæ. They are all marine; and the right whale feeds largely upon some of the species, engulfing great numbers in its open mouth, and straining them from the water by means of its baleen. The Clio borealis of the Arctic Seas is the best known and most interesting example.
4. What substance was once a vegetable, but is now a mineral; was once valued as a medicine, but is now used only for purposes of ornament?
Amber is the fossilized resinous exudation from several species of extinct coniferous trees, of which one, the Pinites succinifer, is supposed to have produced a greater part. It now appears like coal, in connection with beds of which it is usually found, as a product of the mineral kingdom. It formerly had a high reputation as a medicine, but the virtues ascribed to it were almost entirely imaginary. It is usually of a pale yellow color, sometimes reddish or brownish, sometimes transparent, sometimes almost opaque. It is now extensively used for ornaments, and especially for mouthpieces of pipes, the consumption being greatest in Eastern Europe, Turkey, Persia, etc. Fine pieces are worth more than their weight in gold. The largest mass known is in the Royal Cabinet at Berlin; its weight is eighteen pounds, and it is valued at $30,000. Most of the amber of commerce is obtained from the shores of the Baltic, between Königsberg and Memel. It was an article of exchange long anterior to the dawn of history, as we know by its frequent occurrence in the remains of the lake dwellings of Switzerland. The earliest notice of amber we find occurs in Homer’s “Odyssey,” where, in the list of jewels offered by the Phœnicians to the Queen of Syria, occurs “the gold necklace hung with bits of amber” (Od., XV. 460). It becomes negatively electric by friction, and possesses this property in a high degree, which, indeed, was first observed in it, and the term “electricity” is derived from Elektron, the Greek name of amber.
5. How did the ancients account for the origin of amber?
Among the Greek fables purporting to account for the origin of amber, it is narrated that the Heliadæ, on seeing their brother, Phaëthon, hurled by the lightning of Zeus (Jupiter) into the Eridanus, were by the pitying gods transformed into poplar-trees, and the tears they shed were dropped as amber on the shores of the river. A less poetical theory of its origin states that it was formed from the condensed urine of the lynx inhabitating Northern Italy, the pale varieties being produced by the females, while the deeper tints were attributed to the males.
6. What is the value of a pound of steel when made into hair-springs for watches?
A pound of steel that costs but a few cents becomes worth $128,000 in the shape of hair-springs for watches.
7. Who devised the instrument for determining the pressure of the blood in the arteries and veins of the living body?
The Hæmadynamometer (from the Greek αἶμα, blood, δύναμις, force, and μέτρον, a measure) was devised for this purpose by Poisseville. The pressure of the blood is measured, as in the barometer, by the column of mercury that it balances. The instrument has recently been improved in various ways, and a contrivance has been added by which the oscillations of the mercury are inscribed in the form of an undulating curve on a cylinder made to revolve by clock-work; the height of the undulations denoting the pressure, and their horizontal amplitude the time.