to a greater distance than the anticipated striking-distance and gradually approached until the spark passed. The discharger was then detached from the battery, and after reading the scale, connected with a separate battery of 10 cells with a detector-galvanometer in circuit. The terminals were again approached until the motion of the galvanometer indicated contact between them. The scale was again read, and the change in reading gave the required length of spark. With 600, 1200, 1800 and 2400 cells the striking-distances were found to be 0033, 0130, 0345 and 0535 inches. These numbers are nearly proportional to the square of the number of cells, which would give the distances 0033, 0132, 0297, 0528. The length of spark is much influenced by the form of the terminal. Generally a copper-pointed plane was employed and the current reversed 352 times per second by a revolving commutator, or a double key discharger.

When the point was negative, a glow in form like a paraboloid was seen surrounding it long before the spark passed, and as the distance was diminished gradually extending to the positive terminal. With 1800 cells the glow was seen at a distance of 0545 and with 2400 cells at a distance of 0865 inches. Moreover when the disc was positive it became covered with a peach-like bloom which became stronger in the center as the terminals were approached, giving rise to Newton's rings. This effect was next studied with the whole series of 5640 cells. The glow was now visible at 1.073 in. and the spark passed at 139. Replacing the flat disc by one that was slightly convex the glow occurred at 1124 in. and the spark at 140. Reversing, the current gave sparks of 154 and 164 in.

To ascertain whether a current really passed when the glow appeared, vacuum-tubes were interposed when they were illuminated even before the glow appeared. Of course the striking distance was in this case shortened. With a hydrogen tube having a resistance of 190,000 ohms the glow occurred at 939 and the spark at 092 inches. A 31-inch tube was brilliantly illuminated when interposed between one terminal and the battery, when the terminals were separated to the extreme range of the discharger or 1-2 in. and before any glow was visible at the negative electrode. Later a current was obtained with the negative point 5.1 in. distant from a positive plate 6 in. in diameter.

Considerable difficulty was experienced in measuring the resistance of the tubes, and it soon appeared that this resistance rapidly increased as the current passed. After a time, however, they recovered their original resistance. Ultimately it was found to be better to discard the indications of the galvanometer and to rely solely on the appearance of a luminosity in the tubes placed on one side of Wheatstone's bridge as soon as the insertion of a balancing resistance was made in the other. A curious conclusion is derived from the law that the length of spark is proportional to the square of the number of cells, if it proves to be correct. One cell would give a spark about '00000001 in. long while a hundred

thousand which come within the limit of experimental possibility would give a spark about 92 inches long. Probably a million would never be made but they should give a spark 9166 inches or 764 feet long.-Nature, xiii, 277.

E. C. P.

10. Acoustics. Letter to the editors by Professor A. M. MAYER, dated Stevens Institute of Technology, Hoboken, New Jersey, March 17th, 1876.-Gentlemen: Having in hand researches whose completion will occupy several months, I desire to place on record my invention of the two following methods of research. The first is a plan for the determination of the relative intensities of sounds of the same pitch. The second is a method of determining the direction of sounds. I request the privilege of being permitted first to attempt to develop these ideas after I have finished the original work which at present occupies all my leisure.

First method. A loose membrane, or a slip of gold or aluminium foil, is placed anywhere between the centers of origin of two sounds of the same pitch. The plane of this membrane is at right angles to the line connecting these sonorous centers. If both sides of the membrane are simultaneously acted on by sonorous vibrations of the same phase and of equal intensity, the membrane will remain at rest. The above condition is thus attained. Attach to the center of the membrane a short delicate glass thread whose end can be observed through a microscope, or, place a reflecting metallic film on the central part of the membrane so that one can observe the motion of a beam of light reflected therefrom. If we place, at hazard, the membrane between the sonorous centers it is probable that it will be set in vibration. Now if it is moved from its position its vibrations will either increase or decrease in amplitude. Move it in the direction that causes the amplitude of the vibrations to decrease, and until the vibrations have a minimum of swing. The membrane is now in a plane where the phases of vibration are the same but of unequal intensity. The membrane is now moved one-half wave-length either from or toward one of the sonorous centers and is thus brought into another plane of minimum vibration. Thus move the membrane until it is brought into that plane where vibrations of the membrane are either entirely destroyed or have their least amplitude. If the membrane vibrates, then move it and the source of one of the sounds so that they both approach to or recede from the other sonorous center always by the same quantity. This is accomplished by moving a board to which is attached the membrane and one of the sources of sound. By the last adjustment we can soon reach a plane where the membrane remains at rest and where the intensities of the two sonorous vibrations are

equal. It appears that I have thus devised a phonometer which is analogous to the photometer of Bunsen.

The above method appears to me preferable to the phonometer I described in this Journal, Feb., 1873. There are objections to the use of resonators and reflection which I cannot here explain. Second method. If the plane of a free membrane be placed at

right angles to a wave-front it cannot vibrate, for both of its sides are simultaneously acted on by impulses of the same phase and of equal energy. Thus, by bringing the plane of a membrane into that azimuth where it remains at rest we shall have found the plane passing through the center of origin of the sound. also propose the use of two resonators, or of two ear trumpets, placed at the ends of a long horizontal rod which rotates around a vertical axis. I may thus obtain an increase in the aural parallax. By rotating the horizontal rod around its center I may be able to bring the two sonorous sensations either to disappear, or to become of equal intensity, and by these indications to arrive at the direction of a sound. The last mentioned idea may develop into something useful to the mariner who has to ascertain the direction of a fog signal.

II. BOTANY AND ZOOLOGY.

1. Botanical Contributions, separately issued from the current (eleventh) volume of the Proceedings of the American Academy of Arts and Sciences.-These are, first, a series of miscellaneous contributions, characters of new species, and several new genera, mainly Californian, by Asa Gray. The paper begins with the discrimination of two plants which have long been confounded, namely, Sedum pusillum of Michaux and Diamorpha pusilla of Nuttall. They grow together, but are distinct enough in appearance as well as in structure when seen in the living state, as they were by the author of this paper a year ago. There is a revision of the genus Collinsia, of the North American species of Mimulus, twenty-nine in number, and of Monardella, eleven in number.

The other papers are by Sereno Watson. 1. On the Flora of Guadalupe Island, Lower California, founded upon a unique collection of dried plants made by Dr. Edward Palmer. 2. List of the collection with Dr. Palmer's notes upon them. There is a notable amount of new species, and two new genera. These are characterized, as are the new Gamopetala, by Prof. Gray in his paper above mentioned, as to the remainder by Mr. Watson in his third article, entitled, Descriptions of New Species of Plants chiefly Californian, with Revisions of certain Genera. The other new species described and the revisions are mainly such as came to light in Mr. Watson's work on the Polypetala of the Botany of California, soon to be published. Among them are many plants of much interest, such, for instance as second species of the genera Crossosma, Lyrocarpa and Adolphia. Cercidium is shown to belong to Parkinsonia. A revision is made of the North American species of Trifolium, also of Lathyrus and Peucedanum, both very critical works; and the cucurbitaceous genus Megarhiza of Torrey is re-established upon five species. Mr. Watson's descriptions, as usual, are in the English language, an advantage in home but not for foreign use.

A. G.

2. Botanical Necrology of 1875. On the home list only one name recurs to memory, that of

INCREASE ALLEN LAPHAM, LL.D. He died September 14, in the 64th year of his age. A beautiful tribute to his memory, read before the Old Settler's Club, of Milwaukie, by S. S. Sherman, Esq., has just been printed, and is noticed on a following page. An excellent portrait is prefixed.

The following botanists have deceased in Europe:

FRIEDRICH GOTTLIEB BARTLING, one of the oldest professors at Göttingen, a veteran teacher, but not a voluminous author; aged 77.

ALEXANDRE BOREAU, of Angers, France, author of the Flora du Centre de la France.

JOHN EDWARD GRAY, March 7, at the age of 75. Principally known as a zöologist, some of his earliest work was in botany. A notice of his life and services appeared in this Journal, vol. x, p. 78.

JEAN CHARLES MARIE GRENIER, one of the authors of the classical Flora de France, died at Besançon, in the 69th year of his age.

DANIEL HANBURY, died at Clapham, March 24, in his 50th year. A notice appeared in this Journal, vol. ix, p. 75. We learn that his scattered writings are to be collected.

Rudolph FreidRICH HOHENHACHER, died at Kirchheim in Wurtemburg, late in the preceding year, November 14, 1874. He was in early life a missionary at Astrakan, and was afterward in the Caucasian provinces. He was one of the founders of the Unio Itinerario, and he survived his associates, Steudel and Hoch

stetter.

LIEUT. GENERAL JACOBI, the monographer of Agave, died at Berlin, early in the year.

ERNST FERDIND NOLTE, of Kiel, a veteran botanist, who had retired from his professorship a year or two ago, died February 13, at the age of 84.

GUSTAVE THURET, died suddenly at Antibes, France, May 17, at the age of 58. A brief notice of this sad loss was given in vol. x, p. 67. Among other tributes to his memory is one by Rostafinski in the Botanische Zeitung, for July 30. Also one by Professor Farlow in Trimen's Journal of Botany, for January last. ADOLPHE BRONGNIART. We learn that this veteran botanist and vegetable paleontologist died at Paris.

A. G.

3. Life Histories of Animals, including Man, or Outlines of Comparative Embryology; by A. S. PACKARD, Jr. 8vo, 239 pp. with 268 cuts. New York, 1876. (Henry Holt & Co.)- This work consists of a series of papers published in the American Naturalist during the past year, with the addition of a few pages on mammals and nearly three on man. Although, according to the preface, the original papers have undergone "careful revision," we regret to notice many serious errors and inaccurate statements that have been allowed to remain, and are much less excusable in

the permanent book form than in mere magazine articles. Most of these errors must evidently be attributed rather to carelessness in the mode of statement than to lack of knowledge on the part of the author. Thus on page 187, after properly describing the zoëa of crustacea as having only "antennæ, jaws and foot-jaws" for locomotive appendages, he states that he has examined Gelasimi carrying eggs which "contained zoëe, with the two claws alike, and it is probable that the strange inequality in size of the claws in these animals does not show itself until after one or more mouits." What such an incongruous statement means can scarcely be imagined, for the "claws" and other legs are not even formed until a much later period, and it is well known that no such inequality exists in the adult females, nor even in the young males until after they become genuine little fiddler-crabs. On page 216 he says: "the tadpole is much less developed than the larval fish or any other vertebrate; the intestine is not yet formed," but in the next sentence he adds: "It is also a vegetarian, eating decaying leaves; the mouth is small and round, the alimentary canal is remarkably long, the intestine coiled up in a spiral, the mouth is small, destitute of a tongue." On page 157 he says of the Gephyrea: "In none of these worms are there bristles or indications of segments," forgetting the well-marked segments and conspicuous setæ of Echiurus, and the less numerous ones of Thalassema and other genera. On page 120 he says: "There is in the Annelids a dorsal and ventral blood-vessel, the circulatory apparatus being closed and more highly developed than in the Crustacea and Insects, Limulus excepted," but this is by no means true of all Annelids, for in many genera (Polycirrus, etc.,) there are no blood-vessels whatever, and many others have a very imperfect system of vessels. On page 117, fig. 126 is said to represent a later stage of Loligo than fig. 125, but the reverse is true. On page 78 it is said that "in the star-fishes and Holothurians, the alimentary canal opens into five voluminous cæcal appendages," and that these "are in connection with the complicated water tubes" (ambulacral tubes and suckers). The latter statement is entirely erroneous, or at least misleading, and the former is not true of most Holothurians, nor even of all star-fishes. The statement on page 79, that "in those star-fishes in which the alimentary canal is a blind sac, the eggs are emptied into the body cavity" is also incorrect, at least for most species. The statement (p. 70) that "in the Hydroids also the ovaries hang outside the body cavity" is inaccurate, as are also the statements (p. 63) that only one case of multiplication by fission has been observed among Hydroids, and on page 58, that the "ovaries" of Hydra "differ entirely in their mode of formation from the ovaries (gonophores) of the marine Hydroids, which are genuine buds." The account of Physalia (p. 65); that of the growth of septa in Polyps (p. 71); of the development of barnacles (p. 169), and many other paragraphs need revision. The peculiar mode of development of Tubularia, in which the embryo becomes an