Nov. 27, 1873] 



NATURE 



75 



Crystals and Green Mountain Gneisses of the Silurian Age, by 

 Prof. Dana. — Tlie Rev. D. T. Hill gives instances of intelligence 

 in Btifo aiiicricaniis. — Mr. G. W. Moreliouse analyses the struc- 

 ture of the scales ol Lcpisvia sacchariiia. — Mr. D. Scott gives a 

 popular explanation of the differences between the two genera of 

 North American Goatsuckers, the Whippoorwills (Antrosto- 

 mils), and the Nighthawks (CItorddles), which is followed by a 

 short note Irom Mr. Packard, jun., on the Embryology of Li- 

 mulus, with remarks on its affinities. His results are confirma- 

 tory of those of M. Alphonse Milne-Edwards. 



The fourth and concluding part of vol. .xxviii. of the Transac- 

 tions of the Linnean Society, is chiefly occupied by a supple- 

 mentary paper by the Rev. O. P. Cambridge, on New and 

 Rare Biitish Spiders ; but also contains some short papers of 

 importance. — Prof. Oliver descriljes a new genus ol Begoniacea; 

 from New Granada, under the name of Begoinella, a monotypic 

 genus of great interest as respects the geographical distribution of 

 the order ; and three new genera of Malayan plants from the her- 

 barium of Ur. Maingay — Pteleocarpa and Ctenolophon (Olacineo;), 

 and A/aiii:;aya (Hamamelidea;). — Dr. M'Nab publishes his im- 

 portant paper on the Development of tlie flowers of ]Velwilschia 

 miiabilis. Dr. M'Nab considers that in the male flowers of this 

 very remarkable plant we have a very close approach to the 

 Angiosperms, the axis of the flower ending in a mass of tissue 

 which, in the female flower, is tlie terminal ovule ; while, in the 

 female flower, we have the truly gymnospermous condition, 

 there being no carpels, but a terminal ovule, the modified end 

 of the axis of the flower, with a single ovular integument, the 

 pollen grains being applied directly to the naked nucleus. 



SOCIETIES AND ACADEMIES 

 Royal Society, Nov. 20. — "Note on the Electrical Pheno- 

 mena which accompany irritation of the leaf of Diontca miisci- 

 piila" by Dr. J. Burdon Sanderson, F.R.S. 



1. When the opposite ends of a living leaf of Dionaa are 

 placed on non-polarisable electrodes in metallic connection with 

 each other, and a Thomson's reflecting galvanometer of high 

 resistance is introduced into the circuit thus formed, a deflection 

 is observed which indicates the existence of a current from the 

 proximal to the distal end of the leaf. This current I call the 

 iiiviiial leaf-current. If, instead of the leaf, the leafstalk is 

 placed on the electrodes (the leaf remaining united to it) in such 

 a way that the extreme end of the stalk rests on one electrode 

 and a part of the stalk at a certain distance from the leaf on the 

 other, a current is indicated which is opposed to that in the leaf. 

 This I call the stalk-current. To demonstrate these two cur- 

 rents, it is not necessary to expose any cut surface to the 

 electrodes. 



2. In a leaf with the petiole attached, the strength of the cur- 

 lent is determined by the length of the petiole cut off with the 

 leaf, in such a way that the shorter the petiole the greater is the 

 deflection. Thus in a leaf with a petiole an inch long I ob- 

 served a deflection of 40. I then cut off half, then half the 

 remainder, and so on. After these successive amputations, the 

 deflections were respectively 50, 65, go, 120. If in this ex- 

 periment, instead of completely severing the leaf at each time, 

 it is merely all but divided with a sharp knife, the cut surfaces 

 remaining in accurate apposition, the result is exactly the same 

 as if the severance were complete ; no further effect is obtained 

 on separating the parts. 



3. Effect of constant current directed through the petiole on the 

 Av7/-™nY«/.— If theleaf is placed on the galvanometer elec- 

 trodes as before, and the petiole introduced into the circuit of a 

 small Danicll, a commutator being inteqiosed, it is found that 

 on directing the battery-current down the petiole (i.e., from 

 the leaf), the normal deflection is increased ; on directing the 

 current to-.oards the leaf, the deflection is diminished. 



4. Negative variation.— a. If, the leaf being so placed on the 

 electrodes that the normal leaf-current is indicated by a deflection 

 leftwards, a fly is allowed to creep into it, it is observed that the 

 moment the fly reaches the interior (so as to touch the sensitive 

 hairs on the upper surface of tlie Lamina), the needle swmgs to 

 the right, the leaf at the same time closing on the fly. 



b. The fly having been caught does not remain quiet in the 

 leaf ; each time it moves the needle again swings to the right, 

 always coming to rest in a position somewhat farther to the left 

 than before, and then slowly resuming its previous jiosition. 



, . The same series of phenomena present themselves if the 



sensitive hairs of a still expanded leaf are touched with a camel- 

 hair pencil. 



d. If the closed leaf is gently pinched with a pair of forceps 

 with cork points, the effect is the same. 



e. If the leaf-stalk is placed on the electrodes, as before, with 

 the leaf attached to it, the deflection of the needle due to the 

 stalk-current is increased whenever the leaf is irritated in any of 

 the ways above described. 



f. If half the lamina is cut off and the remainder placed on 

 the electrodes, and that part of the concave surface at which the 

 sensitive hairs are situated is touched with a camel-hair pencil, 

 the needle swings to the right as before. 



g. If, the open leaf having been placed on the galvanometer 

 electrodes as in a, one of the concave surfaces is pierced with a 

 pair of pointed platinum electrodes in connection with the op- 

 posite ends of the secondary coil of a Du Bois-Reymond's in- 

 duction apparatus, it is observed that each time that the secon- 

 dary circuit is closed, the needle swings to the right, at once re- 

 suming its former position in the same manner as after mechani- 

 cal irritation. No difference in the effect is observable when the 

 direction of Ihe induced current is reversed. The observation 

 may be repeated any number of times, but no effect is prodiued 

 nnless an intei~'al of from ten to twenty seconds has elapsed since 

 the preceding irritation. 



h. If the part of the concave surface of the leaf which is 

 nearest the petiole is excited, whether electrically or mechan- 

 ically, the swing to tlie riglit (negative variation) is always 

 preceded by a momentary jerk of the needle to the left, i.e. in 

 the direction of the deflection due to the normal leaf-current ; if 

 any other part of the concave surface is irritated, this does not 

 take place. 



i. Whether the leaf is excited mechanically or electrically, an 

 interval of from a quarter to a third of a second intervenes 

 between the act of irritation and the negative variation. 



" On the Algebraical Analogues of Logical Relations," by 

 Alexander J. Ellis, F.R.S. 



The object of this paper is to examine the "mathematical 

 theory of logic," thus laid down by Dr. George Boole in his 

 " Laws of Thought," p. 37 : — " Let us conceive of an Algebra 

 in which the symbols x, y, z, &c. admit indifferently of the 

 values o and i, and of these values alone. The laws, the axioms, 

 and the processes of such an algebra will be identical in their 

 whole extent with the laws, the axioms, and the processes of 

 an Algebra or Logic. Difference of interpretation will alone 

 divide them." For this purpose, fiist the laws of such an 

 algebra have been investigated independently of logic, and 

 secondly the laws of primary and secondary logical propositions 

 as laid down by Dr. Boole, have been developed in an alge- 

 braical form, and compared with the former. The main results 

 presumed to be established are : — 



1. That there is a fundamental difference between such an 

 algebra and logic, inasmuch as the algebra admits of only two 

 phases, o and i , and logic admits of three phases, namely, not 

 only none and all, corresponding to o and I, but also some, 

 "which, though it may include in its meaning all, does not 

 include none'^ (ibid, p. 124), and hence has no analogue in 

 such an algebra ; that is, an algebra of o and I can correspond 

 only to a logic of none and all. 



2. That, notwithstanding this difference, there are certain 

 formal relations of equations which allow the algebra of o and i 

 to be used as an algorithm for the purpose of arriving at certain 

 logical forms, which, however, have then to be interpreted on a 

 basis which has not even any analogy to the algebraical. 



3. That the introduction of this algorithm introduces theo- 

 retical difficulties, adds to the amount of work, and is entirely 

 unnecessary even for the purposes of the theory of probabilities 

 founded upon it by Dr. Boole. 



Mathematical Society, Nov. 13. — Prof. Cayley, and sub- 

 sequently Prof. Sylvester, in the chair. — The following gentlemen 

 have been elected officers of the new council : — President, Dr. 

 Hirst ; Vice-Presidents, Prof. Cayley, and Messrs. Spottiswoode 

 and Sylvester. The retiring members were Prof. Crofton and 

 Mr. J. Stirling, in whose room Mr. Sylvester and Lord Rayleigh 

 were elected. — Mr. Sylvester then gave a description of a 

 new instrument for converting circular into general rectilinear 

 motion, and into motion in conies and other plane curves. 

 (A brief sketch of the historical aspect of the communi- 

 cation, from llie pen of Mr. Sylvester, forms the subject of a 

 paragraph in Nature of Nov. 13.) Several instruments were 

 placed on the table for inspection. — Mr. W. Marshani Adams 



