Oct. 9, i 



NA TURE 



56i 



Animal Intelligence 



Mr. Harrison, like most of those who deal with animal 

 communications, assumes that sounds or words must form 

 the basis. This rests upon the assumption that speech is a. 

 primary system of communication for mankind, instead of being 

 secondary. Many babies will begin with sign communication, 

 and show a preference for it after they are well able to articulate 

 words. The dog will follow human gestures as well as sounds 

 and words. It is indeed worthy of consideration how far signs 

 play a part in communication between animals. Instead of 

 supposing a complicated system of words, as Mr. Harrison does, 

 it is easy to conceive that, with the apparatus he describes, many 

 signs may be made. Expressions of alarm, joy, direction, can 

 be as well made with antenna; as with hands. 



32, St. George's Square, October 6 Hyde Clarke 



Shifting of the Earth's Axis 



Permit me to say that it was from the diagrams in the paper 

 by Mr. Christie which he quotes (Nature, October 2, p. 536) 

 that I drew the conclusions of decrease of latitude. In the 

 fuller statement to which I referred, I had expressly said that it 

 was from the Polaris observations that a decrease of latitude 

 might be deduced. The question turns on whether the truest 

 result is obtained by trusting entirely to Polaris, or by including 

 other stars which are at greater N.P.D. and have more variation 

 in the refraction : as the former is less dependent on the most 

 uncertain element of reduction — refraction — I inclined to rely on 

 it entirely. It would be remarkable if the great oceanic circu- 

 lation should have a mean axis of motion so nearly coincident 

 with that of the earth as not to produce i/iooth of a second 

 change in the Pole during half a century ; the presumption would 

 seem against such a fixity. W. M. Flinders Petrie 



Bromley, Kent 



To Find the Cube of any Nun.ber by Construction 



Capt. H. Brocard (of Montpellier), writing to me on the 

 subject of my note in last week's Nature (p. 539), communi- 

 cates the following two simple constructions : — 



1. On two rectangular axes Ox, O y, take A on Ox and B 

 on Of, such that / OAB = a, through B draw B C _L'' to 

 A B, meeting X in C, and draw CD j_ r B C, meeting O V in 

 D : join A D. Then tan O A D = tan' a. 



2. Take B O D = a, from A on O £> erect _L " to meet B 

 in B : draw B D J_ " to B, and let fall A C ± r to B D. Then 

 if we take A' = unity (A' is the projection of A on OB), 

 BC = ta.na, A' B = tan 2 a, C D = tan 3 a. 



It may be of interest to note with reference to the figure 

 indicated in my construction, that M. Brocard finds that if 

 FK i_ r FD meets CB in K, and A'L±'FA~ meets FO 

 {± r B C) in L, then L D passes through H. 



October 6 R. Tucker 



THE ASCENT OF WA TER IN PLANTS 

 T > HE fact that water is taken up by plants and passes 

 *■ off as vapour at the leaves is one of the best known 

 data of vegetable physiology. The current of water 

 passing up the stem of the transpiring plant is known, 

 moreover, to be copious and rapid, and to pass through 

 certain parts of the wood only. Apart from other ques- 

 tions, it has long been sought to explain by what forces 

 this current can be maintained in the plant, and the diffi- 

 culties which have arisen and been surmounted have been 

 many ; certain of these difficulties, however, are still 

 outstanding. 



It was an immense stride forwards when the fact was 

 demonstrated that the water absorbed by the roots passes 

 up the stem in ihe younger wood ; and when it was 

 recognised that in the Conifers this consists of definite 

 elongated cells, not openly communicating, and is not 

 complicated by the presence of vessels, &c, the problem 

 promised to be much simpler. 



As is now well known, the earlier hypotheses which 

 were made to explain the ascent of water in transpiration 

 have been long put aside, as new facts were observed 

 which could not be satisfactorily explained by them : the 



old theory of capillarity succumbs evidently to the facts ; 

 and Quincke's hypothesis, though less easily despatched, 

 must also be relegated to the list of past errors. 



Two theories, or rather hypotheses, have attracted so 

 much attention lately, that we may fairly regard them as 

 the two rival views for the explanation of the ascent of 

 the transpiration current. The one, especially advocated 

 in its earlier shape by Boehm, seeks to explain the ascent 

 as due essentially to the pressure of the atmosphere 

 acting on a system of air-bubbles and water which can be 

 shown to exist in the plant : this hypothesis, but shortly 

 stated here, is obviously in contradiction to several im- 

 portant facts, e.g. the height of tall trees, and the difficulty 

 of explaining how the atmospheric pressure could act on 

 the closed system of the plant. 



The second, and very different hypothesis, is the one 

 recently proposed by Sachs. Assuming that the mole- 

 cules of water imbibed by the wood cell-walls are held 

 between the complex molecules of these walls in a peculiar 

 condition — very much, in fact, as salt molecules are held 

 between the molecules of water in the sea — then the diffi- 

 culties in connection with tall trees disappear ; for by the 

 peculiar properties of the wood cell-walls it matters not 

 whether a given molecule of water is a yard or a hundred 

 yards high. This hypothesis undoubtedly explains nume- 

 rous facts, and, if choice lay between it and the theory of 

 atmospheric pressure only, no doubt could exist as to 

 which we should accept ; nevertheless, there are objec- 

 tions to it apart from the assumption of such very peculiar 

 properties of lignified walls. 



Before saying anything as to the possible modifications 

 of the former theory, it will be well to see how it arose in 

 the first instance. 



Jamin, in the Comptes Rendus for i860, published an 

 investigation on some capillary phenomena, and particu- 

 larly on the behaviour of capillary tubes containing air- 

 bubbles in addiiion to water. 



Suppose an open capillary tube of glass filled with 

 alternating drops of water and bubbles of air. If pressure 

 is exerted at the one open end of such a tube, of con- 

 siderable length, it is observed that the pressure is not 

 transmitted simply through the system, but that each 

 successive one of the alternating columns of water causes 

 a lessening of the effect. Of course each column of water, 

 between two air-bubbles, has two concave ends, and the 

 changes produced in these can be observed. Without 

 here going into the explanation of this phenomenon of the 

 apparent disappearance of the pressure, it suffices for our 

 purpose that an open column consisting of air-bubbles 

 alternating with drops of water may be placed upright 

 and the water not flow out. Jamin showed that with long 

 tubes, the water-columns of which were sufficiently broken 

 by air-bubbles, even a pressure of three atmospheres 

 applied to one end fiiled to move the lower parts of the 

 column. Such a column of alternating drops of water 

 and air bubbles is called a " ckapelet de Jamin." 



It is known that porous bodies, such as gypsum, absorb 

 water with great force : such bodies when saturated with 

 water are very impervious to air, a fact which may be 

 illustrated by means of the wet linen in any wash-tub. 

 Jamin even proposed an explanation of the ascent of 

 water in accordance with these facts, regarding the wood 

 simply as a porous body. 



It is not necessary to go into details as to the various 

 modifications of the theories which in any way depended 

 upon ordinary capillary phenomena ; enough that the 

 objection that, even if the plant had capillary tubes suffi- 

 ciently fine to support the water columns required by a 

 tall tree, the water could not flow through them so rapidly 

 as the requirements of respiration demand seemed fatal 

 to any of these theories, and made Sachs's assumption 

 of the extraordinary properties of wood cell-walls appear 

 the more necessary. Moreover, the Conifers have no 

 such capillary tubes in the secondary wood. 



