OcTOIiER lit, 18S3.] 



SCIENCE. 



545 



however, are statements which ought to be 

 changed in a second edition. Tiie Zygncniae 

 are erroneously described as producing zo- 

 osjiores (p. 5), — a statement true enough of 

 their rehilives the Confervae, but not of any 

 of tlie Zygnemae. Of roots it is said positive- 

 ly (in italics, p. 21*) that ■ they are never green,' 

 which, to say the least, is a strong statement. 

 On p. 31 we find that '■ in some plants the calyx 

 or corolla is entirel}' wanting, in which case the 

 floral covering is called the perianth," which 

 is certainly not in accordance with ordinarj' 

 usage. On the same page the stigma is curious- 

 ly described as ' the surface of the style.' The 

 Equiseta are not leafless, as they are said to 

 be on p. 104. Their leaves are small, it is 

 true ; but certainly the whorls of united leaves 

 at each joint are evident enough to even the 

 casual observer. The formation of the zvgo- 



spore in Mucor is not correctly given on p. 184, 

 where it is described as resulting from the 

 union of two aerial hyphae. On p. 192, in 

 describing the fl\' fungus, the reader is given 

 the impression that a mycelium u[)on a surface 

 (as a window-pane) attacks its hapless vic- 

 tim, the fl}", which, when dead, is said to be 

 '• standing upon a mat of delicate silk threads 

 spread upon the glass." 



Fig. 21 (repeated in tig. 143) is erroneous 

 in showing the hyphae of the potato fungus 

 to be septated. Fig. 104 is said to show the 

 antheridia of a moss ; but certainly no such 

 organs are visible in the cut given. 



In spite of the slips noted above, and others 

 which we mav well pass over, the little book is 

 a pleasant one to read, and we feel sure that 

 it will receive a hearty welcome from plant- 

 lovers everywhere. 



WEEKLY SUMMARY OF THE PROGRESS OF SCIENCE. 



ASTRONOMY. 



Saturn's rings. — Euoke's division in the outer 

 ring of Saturn has been examined by JI. SchiaparelU, 

 who finds tliat the position and lack of symmetry 

 are the same as previously noticed, but the line is 

 broader, and more diffused than in ISSl. He thinks 

 the phenomenon is variable, and accounts for it by 

 supposing the middle of the ring to be thinner, and 

 by the change of orbit of the particles composing 

 it. He also examined carefully the region about 

 the inner bright ring and the dark ring. At times 

 O. Struve's division was seen very distinctly, and 

 on other occasions very faintly. More observations 

 are necessary to determine whether the phenomenon 

 is variable. — (Oftserp., Aug. ; Astr. nachr., 2,521.) 

 M. Mcx. [289 



The great comet of 1882. — Mr. Maxwell Hall 

 shows the possible identity of the great comet of 

 1882, the comets of I860, isii, and 1608, with a comet 

 which appeared B.C. 370, and which was said to have 

 separated hito two parts. The orbits of all are nearly 

 identical. Taking a period not greatly different from 

 that given by Prof. Frisby for the comet of 1882, he 

 identifies the comets of B.C. 370 and A. U. 1843 with 

 one which was seen in 1100. No comet is recorded 

 for .\.D. 3&S. The comets of 1880 and 1882 may pos- 

 sibly bo identical with two which appeared in 1131 

 and 1132, and with the second part of the comet of 

 B.C. 370. If this is the case, this comet also prob- 

 ably separated into two parts at its unreconled ap- 

 pearance in A.D. .381 or 382. We already have an 

 instance of this separation in Biela's comet; and the 

 comet of 1882 gave evidence, to a certain extent, that 

 a proci>>s of di^integration was going on. — {Observ., 

 Aus;.) M. Mrv. [290 



PHYSICS. 

 Electricity, 

 Atmospheric electricity. — Dr. L. J. Blake has 

 found that no convection of electricity takes place by 

 the rising vapor from a charged liquid surface, to 

 which he gave a potential due to from' four to five 

 hundred Daniells cells. The plate placed in the track 

 of the vapors was, in the different experiments, either 

 colder than the vapor, or of the same temperature. By 

 connecting the liquid with the electrometer, he finds 

 a small negative charge, increasing during the fifteen 

 minutes which each experiment lasted, but not suffi- 

 ciently to justify the statement that electricity is gen- 

 erated by evaporation. In all the work, the lamp was 

 removed before connecting with the electrometer ; and 

 the whole apparatus was within a metallic covering 

 connected with the earth. Distilled water, sea-water 

 from the North Sea, alcohol, dilute sulphuric acid, 

 mercury, and solutions of a number of different salts, 

 were tried. — {A>in. phys. chem., xix. .518.) [291 



ENGINEERING. 



A neMW current-meter. — Mr. L. d'Auria pro- 

 poses an apparatus fur (Ktermining the mean velocity 

 at any vertical in a stream, which apparatus consists 

 of a scow, or pontoon, to be moored in the desired 

 pl.ace; a pole with a pulley near each, end, carrying 

 an endless cord; a light ball; and a species of net, or 

 grillage. The pole is thrust to the bottom alongside 

 the scow, at the point where the velocity is to be 

 gauged ; and the ball is lightly attached to the cord by 

 a string, so as to be disengaged by a moderate pull 

 when it reaches the pulley .at the bottom. The time 

 of the disengaging pull is noted, and also the time of 

 the appearance of the ball at the surface. As the 



