poisonous property of the sting of bees lies in the formic acid it discharges, which is also "probably associated with some other toxic agent." The idea that the bee invariably dies after stinging is a vulgar error. "It will, if allowed time, generally carry its sting away by traveling round upon the wound, giving the instrument a screw-movement until it is free." More usually, however, the bee is not allowed time to travel round, "and she loses not only the sting and the venom-gland and sac, but also the lower portion of the bowel, so that her death follows in an hour or two." We are further informed that no bee inflicts a wound "until she has examined the nature of the surface to be punctured, using a pair of very beautiful organs called palpi, elaborately provided with feeling hairs and thin nerve-ends."
Mr. Edison's Pyromagnetic Dynamo.—Mr. Edison, in his paper, at the American Association, on the "Pyromagnetic Dynamo," after describing the construction and operation of the machine, said that the results thus far obtained lead to the conclusion that the economy of production of electric energy from fuel by the pyromagnetic dynamo will be at least equal to, and probably greater than, that of any of the methods in present use. But the actual output of the dynamo will be less than that of an ordinary dynamo of the same weight. To furnish thirty sixteen-candle lights in a dwelling-house would probably require a pyromagnetic generator weighing two or three tons. Since, however, the new dynamo will not interfere with using the excess of energy of the coal for warming the house itself, and, since there is no attendance needed to keep it running, there would seem to be already a large field of usefulness for it. Moreover, by using the regenerative principle in connection with it, great improvement may be made in its capacity, and its practical utility may very probably equal the interesting scientific principle which it embodies.
Characteristics of Tropical Woods.—Professor R. H. Thurston, describing some Nicaraguan woods in the American Association, said that the tropical and sub-tropical woods are distinguished usually by their extraordinary size, strength, hardness, and solidity, as well as by durability, as against both weather and the attacks of insects. About thirty samples, selected simply by considerations of convenience and previous acquaintance from among an enormous number of probably equally valuable genera, were subjected by the author to special tests. Some of them resembled in appearance and quality mahogany; some, our own yellow pine; others, the oaks and other hard woods of our forests, but excelled them in density, strength, elasticity, and durability. While they may prove of extraordinary value for many purposes, they are often so hard to work that their usefulness is likely to be restricted. The Central American forests contain an enormous store of timber of remarkably fine quality.
Exceptions to the Rule of Laissez-Faire.—Professor Sidgwick read an elaborate paper in the British Association on the economic exceptions to the laissez-faire. Political economy, he said, as commonly understood, includes a general argument showing how wealth tends to be produced most amply and economically in a society in which government confines itself to the protection of person and property and the enforcement of contracts not brought about by force or fraud, leaving individuals free to produce and transfer to others whatever utilities they choose on any terms that may be freely arranged. The argument is, briefly, that in a society so constituted, the regard for self-interest on the part of consumers will lead to the effectual demand of the things that are most useful, and the regard for self-interest on the part of producers will lead to their production at the least cost. It is, however, now generally held that the broad rule of "leave alone," to which the argument points, must in practice be limited by various exceptions. Two classes of these exceptions are distinguished, viz.: (a) those which are due to the limitations under which abstract economic theory has to be applied in the art of government; and (b) those which it is the more direct business of economic theory to analyze and systematize. In class (a) may be distinguished—(1) governmental interference to regulate the education or employment of children; (2) interference for the promo-