SCIENCE. 



157 



of the ecliptic whose longest and shortest day, for our nor- 

 thern hemisphere, would coincide with the north and south 

 plane, passing through the Alpine focus and also through 

 the node of intersection for the terrestrial and magnetic 

 Equator. This gives us one great circle from Behring's 

 Straits to its antipodal Antarctic, due south from Mt. Rosa; 

 the other from Scandinavia, at the Arctic Circle, to the an- 

 tipodal point on the Antarctic, which will be found due 

 south from Behring's Straits. As these ran through the 

 northern hemisphere, the course of one from the volcanoes 

 of Sumatra is nearly parallel to the formerly described Asi- 

 atic continental trend as well as the Japan Gulf Stream, and 

 nearly parallel again through North and South America to 

 said Asiatic trend prolonged, whereby a region is inclosed 

 of Nevada geysers, New Madrid earthquake region, Arkan- 

 sas and Virginia hot springs, Cuban, Venezuelan, Grena- 

 dan, Peruvian, and Chilean volcanic and earthquake re- 

 gions. The course of the other, while running nearly par- 

 allel to the North American east coast trend, is from the 

 thirty-nine volcanoes (see Dana's Manual, p. 703) of Cen- 

 tral America to the geyser and volcanoes of Iceland, thus 

 inclosing between it and the North American trend our 

 Gulf Stream, probably even aiding to heat it; while on the 

 opposite side of the globe the inclosed line embraces the 

 Hindoo Cush and Western Himalaya elevations; the dis- 

 turbed regions of Hindostan and islands in the Bay of Ben- 

 gal (some brought up within the Historical Period) as well 

 as the numerous volcanoes of Sumatra. 



The evident connection of these laws with Terrestrial 

 Magnetism, Mining and Mineralogy, Archaeology and Eth- 

 nology, is left for future discussion. 



AN INVESTIGATION OF THE VIBRATIONS OF 

 PLATES VIBRATED AT THE CENTRE. 



By ThomAs R. Baker. 



Most of the plates used were window panes of various 

 shapes and sizes. They were vibrated by rubbing an at- 

 tached glass rod. The tubes, which were about -j\ of an 

 inch in diameter and 20 inches long, were attached at right 

 angles to the face of the plate with sealing wax. The sup- 

 port for the plate was a rubber cap, the common lead-pencil 

 eraser, fitted on the end of a post projecting from a disk of 

 lead. A short rubber-capped lead pencil fixed upright in a 

 wooden block answers the purpose just as well. 



The plate was balanced on the support, the tube standing 

 upright and held loosely between the thumb and forefinger 

 of the left hand. Then catching the tube between the moist- 

 ened thumb and forefinger of the right hand and rubbing 

 downward the vibrations of the plate were produced. 



Different tones were obtained from the same plate by va- 

 rying the pressure and the position of the thumb and finger. 

 Each plate yielded from one to six tones, the number increa- 

 sing with the size and thinness of the plate. A plate 10 in. 

 by 14 gave six tones, one 4X4 gave two, and one 3X3 gave 

 but one. 



The interval between the lowest and second tones of a 

 10X12 plate was two octaves and one tone; between the sec- 

 ond and third, a diminished sixth; and between the third 

 and fourth, an augmented fourth. The greatest interval 

 found between the lowest and highest tones of a plate was 

 more than four octaves, and the greatest interval observed, 

 considering the tones of all the plates tried, was more than 

 five octaves. 



Plates were reduced in size by cutting strips an inch 

 broad from them, and a test was made of the tones of each 

 plate thus produced. A plate 12 inches square was cut 

 down to n in. by 12, then to 10x10, and so on until it was 

 reduced to one 2 inches square. By this operation there 

 was furnished a series of eleven plates closely alike in 

 thickness and structure. 



The intervals between consecutive tones of each plate of 

 this series down to the plate 7x7 were almost uniform, 

 namely ; two octaves and a fourth between the lowest and 

 2nd tones, a seventh between the 2nd and 3d, and a fourth 

 between the 3d and 4th. From the plate 8x8 to that 3x3 



the intervals between the lowest aud 2nd tones were almost 

 uniform, being about one octave and a fourth. The other in- 

 tervals were variable. The difference in pitch of corres- 

 ponding tones of consecutive plates was with few excep- 

 tions, uniform down to the plate 7x7, namely ; three semi- 

 tones. 



The following is a summary of the facts derived from 

 these experiments : 1. The difference in pitch of the lowest 

 and 2nd tones of all plates tried between the sizes 10 in. by 

 14, and 7 in. by 7, was two octaves to two octaves and a fourth, 

 and the difference in pitch of corresponding tones of square 

 plates between the sizes 8 in. by 8, and 3 in. by 3 was one 

 octave and a fourth. 2. The intervals between the tones 

 of plates giving not more than five tones diminished as the 

 pitch increased, but this was not true of plates giving more 

 than five tones. 3. The pitch of tones given by a series of 

 plates which varied in size as the square of a series of num- 

 bers whose common difference is one made a sudden leap 

 from one uniform scale to another. 



The forms of these variations were learned in the usual 

 way by vibrating the plates with sand sprinkled over them. 

 The figures were copied by placing the plate over paper 

 which had been wet with a solution of potassium bichro- 

 mate and dried in the dark. The plate and paper were ex- 

 posed to diffused light or to the vertical rays of the sun. 

 The paper not hid by the sand soon darkened and when 

 this change had taken place the plate was removed and a 

 lead pencil run along the bands of lighter colored paper 

 representing the sand lines. This paper was then placed on 

 white paper and the figures copied by pressure. About 150 

 sand figures were copied and traced. 



The vibrating of plates at the centre as here described, 

 seems to be the best method for class illustration, the main 

 object being to show the formation of sand figures. To 

 vibrate a plate at the centre in this way, expensive appara- 

 tus is not needed, a pane of window glass, a glass tube and 

 a rubber eraser — the essential articles — being procured at 

 the cost of a few cents. To vibrate a plate in the ordinary 

 way, a clamp and bow costing several dollars are necessary. 

 Moreover a plate vibrated at the centre will, I think, yield 

 to the ordinary experimenter more tones than one vibrated at 

 the edge. 



A simple method of showing the vibration in parts of a 

 rod and a string was suggested by the vibrating plate. 



The end of a piece of glass tubing was drawn into a long 

 fine thread, and the tube attached with sealing wax to a long 

 narrow plate near one end. Then when the plate was vi- 

 brated so as to yield a low tone, the glass thread vibrates in 

 parts forming a series of spindle-like segments. 



A piece of sewing thread was stretched from one end of 

 the narrow plate to the other over the free end of the vibra- 

 ting rod and fastened to the plate with bees-wax. Then at 

 a low tone of the plate the thread vibrated in segments. 



TYPES OF POTTERY. 



By Prof. Edw. S. Morse. 



The earlier types belonging to the shell heaps of Japan 

 were described and illustrated by specimens from each of the 

 deposits examined by Prof. Morse and his special students. 



The pottery of Yeso was nearly all cord-marked, while 

 the shell heap pottery of the middle of Japan had a much 

 less proportion cord-marked. 



In the southern portions of Japan, at Higo, cord-marked 

 pottery was extremely rare. 



He remarked on the extreme diversity in the shape and 

 ornamentation of the pottery in different places in japan, 



The pottery of Yeso resembling the pottery of the North- 

 ern United States ; the pottery from the central portions of 

 Japan finding their resemblance to the pottery found in 

 Porto Rico and Jamaica. He also spoke of the hard blue 

 pottery supposed to be Korean, and associated with it a red 

 pottery, which might have been made by the same people. 

 This was lathed-turned. Other forms were mentioned and 

 illustrated by examples. 



