July 18, 1884." 



SCIENCE. 



51 



Under as recent a classification as that adopted by 

 Lankester, in the new edition of the Encyclopaedia 

 Britannica, this creature would form a new order, 

 Ainyaria, as opposed to the old Mono- and Dimy-aria. 

 These orders being pretty generally given up, though 

 not yet out of the text-books, it is probable that no 

 others can yet be formulated. Whatever be its rela- 

 tions to the higher groups, a point to be determined 

 by further study, there can be no doubt that the ani- 

 mal forms the type of a new family, Chlamydoconchae, 

 and may take the name of Chlamydoconcha Orcutti. 

 It is evident already, that the genus does nothing 

 toward bridging the gap between the gastropods and 

 pelecypods, but is simply a remarkably aberrant form 

 of the latter group, and probably derived from some 

 form with an external shell. It is able, according to 

 Mr. Orcutt, by sphincter-like contractions of the man- 

 tle, to produce currents of water over the gills, which 

 are probably finally ejected by the anal tube. 



A paper on the subject, with figures, will be pub- 

 lished shortly. AVm. H. Dall. 



Time without instruments. 



Students usually feel little interest in the method 

 of time in astronomy by 'a single altitude of the 

 sun,' because they do not expect to own an instru- 

 ment with which to measure the altitude. They 

 ean easily make the apparatus described below, by 

 which, with careful handling, time may be found 

 with a probable error of fifteen seconds. 



Frame together the three pieces AB, AC, and BE, 

 at right angles, — AB about sixty inches, AC eigh- 

 teen inches and a half, and BE ten inches long, and 

 each an inch and a quarter square. Cut a half-inch 

 slit, one inch deep, in the end C, and in the direction 

 AB. Fasten a piece of tin one inch square, with a 

 hole an eighth of an inch in diameter, on the right- 

 hand face of AC at C, with its hole opposite the 

 centre of the slit. Set in a bubble at I by which to 

 level AB. Let fall a perpendicular from the hole in 

 the tin plate to AB ; and at about twelve inches from 

 the foot of that perpendicular commence the gradu- 

 ation on the centre line AB, dividing into inches and 

 half-inches, and numbering 12, 13, etc., towards B. 

 It will be well to paste a strip of drawing-paper on 

 the face AB, on which to make the graduation. 



Measure once for all the exact height in inches of 

 the centre of the hole in the tin plate above the 

 upper face of AB, which should be about eighteen 

 inches, and multiply it by the decimal .9994358, 

 which product designate by h. By using this for the 

 height of AC, all altitudes will be corrected for mean 

 refraction. 



To use it, place in the sunlight, — best when the sun 

 is not less than 16° nor more than 45° high, — with 

 AB levelled by the. bubble, estimating by eye when 

 AC is rjerpendicular, so that the bright spot from the 

 hole in the tin shall fall on the graduated centre 

 line of AB. With watch in hand, read the hour, 



minute, and second when the centre of the elliptical 

 bright spot is exactly on some dividing-line of the 

 scale, and call the scale-reading r : then the sine of 



h 

 the sun's altitude = , = sin a. 



vr* + w- 



For the hour-angle = P, the most convenient for- 

 mula is, — letting o = sun's declination, and I = the 



sin a — sin 6 sin I 



latitude of the place, — cos P — — n „ a A nr ^ B , — 



1 ' cos o cos I 



This formula, with the known latitude (say. 30° 12' 

 45"), may be put in the form 



log cos P = log { sin a — [9.77143] sin 8 } + a. c. log cos 6 + 0.00322. 



A nautical almanac is needed for declination and 

 the equation of time, though tabulated mean values 

 of these for every tenth day of the year will answer 

 for the usual accuracy required in common local 

 time. 



The form of apparatus may be varied to suit thf 1 

 taste of the student, or he may use the tin disk with 

 a plumb-line suspended from it, in connection with a 

 straight-edge levelled by a carpenter's level, and these 

 of any lengths he chooses. 



Time by ' equal altitudes of the sun ' may be found 

 by the same device. 



A. H. Buchanan. 



Cumberland university, Lebanon, Tenn., 

 July 4. 



Rotation experiments on germinating plants. 



The opposite growth of the root and stem of a 

 germinating plantlet, under other influences than that 

 of gravity, we have recently shown by the following 

 experiments. A circular trough (seen in section. 

 hi), fig. 1) some sixteen inches in diameter and three 



m h 



MM 



Fig. 1. 



deep, rotates about the vertical axis a a. The trough, 

 closely filled with earth, was planted with a quantity 

 of well-soaked beans and seed-corn, and the whole 

 covered with the fine gauze represented by the dotted 

 lines. Forty-eight hours were allowed for the seeds 

 to begin their growth, before the trough was started 

 in rotation. By means of a Tuerk's motor, a uniform 

 and continuous motion, at the rate of one hundred 

 and eighty revolutions per minute, was then main- 

 tained for four days. At the end of this time the earth 

 was carefully removed, and the positions of the young- 

 plants precisely noted. It was universally observed 

 that the stems were accurately directed towards the 

 axis, and the roots towards the circumference, of 

 the trough. Figs. 2-6 represent several specimens. 

 A B is the horizontal, A being towards axis, and 

 B towards circumference ; those of figs. 2, 5, and 6, 

 were at a radius of six inches from axis; figs. 3 and 

 4 had radii of five and four inches. The curves 

 at the points C, C, C, C, are quite significant, being 

 the points to which the radicals had extended before 



