of the most complex and arduous astronomical questions. He was a member of the commission to observe the great solar eclipse of 1868 and the transits of Venus of 1874 and 1882. His most considerable book was the Traité de Mecanique Céleste, which was published in 1890, and has become an authority on the subject. His other principal books are the Lunar Tables; a treatise on the Movement of the Planets around the Sun, according to Weber's Electrodynamic Law; a work on Shooting Stars; Observations of the Sun Spots at Toulouse in 1874 and 1875; and a collection of Exercises on the Infinitesimal Calculus.
Bacteriologists, says Sir Joseph Lister, are now universally agreed that, although various other conditions are necessary to the production of an attack of cholera than the mere presence of Koch's comma bacillus or vibrio, yet it is the essential substance of the disease; and it is by the aid of the diagnosis which its presence in any case of true cholera enables the bacteriologist to make that threatened invasions of this awful disease have of late years been so successfully repelled from English shores. "If bacteriology had done nothing more for us than this, it might well have earned our gratitude."
The observation made by Mr. Alfred Springer five years ago that the acoustical properties of aluminum are approximate to those of wood, has been verified by continued experiments with sound-boards of that metal, and the author exhibited in the American Association several aluminum violins, together with a device, called a bass bar, by means of which the quality of the tone produced by the instrument can be controlled.
According to President T. Kirk, of the Wellington (New Zealand) Philosophical Society, the chief agents, next to man, in the destruction of native species of plants in the colony, whereby the way is cleared for introduced species, are sheep, rabbits, and the black rat. These animals have almost laid several districts bare, leaving only the sturdiest and most persistent growers. Introduced plants—silenes, white-weed, docks and sorrels, chess, and velvet grass—have nearly driven out the original littoral vegetation in some places. Even more destructive are the ravages caused by the parasites which these strangers bring with them. While the first catalogue of naturalized plants in New Zealand, published in 1855, comprised forty-four species, the present number is put by Mr. Kirk at three hundred and four, and by others at three hundred and eighty-two.
The ruins of Tepoztlan are regarded by Mr. H. Saville as especially important because they are the only American ruins to which a definite date can be attached. The sign of Ahuizotl, the immediate predecessor of Montezuma, is engraved on one of two slabs in the walls, and on the other the date, ten Tochtli, which corresponds to 1502.
Dr. H. C. Hovey called attention in the American Association to certain old monuments in colonial graveyards, particularly at Byfield and Newbury, Mass., and also to some milestones and stones in the foundations of old houses, which were carved in a style very unlike that of Puritan monuments. The symbols on them are pagan rather than Christian, and include disks, whorls, fleur-de-lis, phallic signs, and a design representing the sun-gods' bride with a sunburst over it. It may be suggested as a solution of the enigma they present that the maker of them had seen figures of the kind somewhere, or pictures of them, and copied them in the desire to offer something new and striking.
In one of his papers on the history of Niagara Falls, read in the American Association, Mr. G. K. Gilbert presented evidence of a former outlet of Lake Algonkin draining the upper lakes, heading at Kirkfield, Ontario, and following the Trent River to Lake Ontario, which belonged to an earlier date than the outlet through Lake Nipissing and the Ottawa River. There appear, therefore, to have been two periods after the origin of the Niagara River in which it was an outlet for the Erie basin only, and did not carry the waters of the upper lakes.
The making of the Mammoth Cave is attributed by the Rev. H. C. Hovey, D. D., in a paper read before the American Association, wholly to the solvent action of water upon the limestone. No earthquake disturbance or pot-hole action in the deep parts of the cave can be considered as having had any important effect upon the excavation.
"What is the bark?" is asked in a paper read before the American Association by C. R. Barnes, who calls attention to the varying use made of the term bark by different botanists. The Germans use Borke and Rinde to denote respectively the external tissue of the root or stem which dries up, and the entire mass of tissue outside the cambium. In this they are followed by the English; and the American usage, except as modified by foreign influence, assigns the name bark to the entire mass of tissue outside the cambium. In this use we are followed by the French. The author advocated