Page:Science vol. 5.djvu/238

218 and below a mountain, or within any other extended region. The difficulty in the way of utilizing the masses of lead is the extreme minuteness of the attraction exerted by any manageable mass. On the whole, however, the latter method, in the bands of Balley, Reich, and others, has been the more reliable of the two. A few years since, the late Professor Von Jolly of Munich undertook to measure the attraction of a globe of lead about one metre in diameter, upon a weight in the pan of a balance. The arm of the balance was at a height of twenty-one metres over the leaden globe, and the pan which held the weight was suspended by a wire of that length. It was balanced by a weight in the other pan immediately below the balance, so that the attraction was exerted only upon one weight.

A modification of Jolly's method was recently described In a paper read before the Berlin academy of sciences, by Arthur König and Franz Richarz. These gentlemen propose the following modification of the long suspension. They will cast a great block of lead in the shape of a parallelopiped. On the horizontal surface of this block will be placed an ordinary balance, the scales of which shall swing very near the surface. A vertical hole will be bored through the block, directly under the point of suspension of each scale of the balance; and a second pair of scale-pans will be suspended below the block by wires attached to the upper scale-pans, and passing through these openings. Thus the balance will consist of two pairs of scale-pans,—one pair below, the other above,—with the leaden mass between them. The masses whose attraction is to be measured will be placed, the one in the upper, and the other in the opposite, lower, pan of the scales. The attraction of the block will make the lower one lighter, and the upper one heavier. The positions will then be changed by removing the weight in the lower pan to the pan immediately above it, and vice versa. Then the attraction of the block will make heavier the weight which was before lighter, and vice versa, thus causing a difference in the weights amounting to four times the attraction of the block.

It is proper to add that this weighing method is subject to a good deal of criticism. So far as we are aware, its original inventor was Mr. C. S. Peirce, who proposed to utilize the Hoosac tunnel for the purpose,—to bore a hole from the surface of the earth vertically to the tunnel, and use it for the passage of a wire to hold a weight supported by a balance at the surface. It was found, however, that the air-currents, and other sources of disturbances, were such as to render the method inapplicable. It is difficult to see how Von Jolly's apparatus could have been free from the same difficulty. The attraction of his leaden sphere could only have been one five-millionth part of the weight,—a fraction which is about the extreme limit with which it is possible to effect a weighing under the most favorable conditions. With a block of any manageable size, the attraction by the method of König and Richarz will hardly reach a millionth part of the weight. Still the authors are making arrangements to execute their experiment, and physicists will look with interest for its result.

prehistoric studies in Portugal of the late lamented Carlos Ribeiro have already been brought to our readers' notice (Science, Dec. 14, 1883). He was the leading spirit at the Lisbon congress, as well aa its general secretary; and his long illness dating from that time, and his death, which took place Nov. 13, 1882, account for the delay in the appearance of this long-expected official report. It has now been given to the world in the most satisfactory manner, with beautiful typography and ample illustrations, under the charge of Sig. Delgado, who has succeeded to the position of director of the Geological bureau of Portugal. The freshness of it, however, is somewhat impaired, owing to the full résumé of the proceedings, that was given by Cartailhac in tha Matériaux, November and December, 1880, and by Professor Bellucci, at even greater length, in L'archivio per l'antropologia, e l'etnologia, vol. xi. fasc. 3.

It was understood that the chief interest of this congress would centre about the discussion of the first question proposed: "Are there any proofs of the existence of man in Portugal during the tertiary epoch?" Ribeiro and the Portuguese geologists desired that foreign geologists and prehistoric archeologists should visit and thoroughly study at least one of the localities from which the supposed tertiary flints had mainly come. All this was accomplished, and the results are already well known. An excursion (somewhat of the nature of a picnic) was made to 'the desert of Otta,' about thirty miles north of Lisbon, where Professor Bellucci of Perugia found in place, in a miocene deposit, a flint flake with a well-marked 'bulb of percussion.' This was seen by several witnesses before it was detached, and by many experts was pronounced to be of undoubted human origin. To the writer, however, the engraved figure of it does not appear entirely convincing. Upon their return, the series of flint objects discovered in this locality by Ribeiro, during the past twenty years, was submitted to the judgment of a commission of nine experts. Their report, and the discussion that ensued thereupon, developed a great diference of opinion. Upon the geological question all were in accord with the Portuguese geologists, that the locality was the shore of a miocene lake. In regard to the archeological