K 



NATURE 



\June 29, 1882 



Himalayan zone is found to be associated, not only with the 

 subsequent conditions already named, but also with an initially, 

 and therefore according to experience subsequently weak south- 

 west monsoon, which in its turn invariably causes local, if 

 not general drought and famine. These heavy snowfalls are 

 found to have a tendency to recur at the minimum sun-spot 

 epochs, and are proximately due to some condition of the upper 

 anti-monsoon current, at present not exactly known, by which a 

 larger amount of vapour is deposited in the winter, on the 

 Himalaya as snow, and on the North Indian plains as the 

 " winter rains." 



It does not appear that we can so readily account for the 

 occurrence of the present ice-floes off Ireland or for the large 

 masses which have been encountered this spring in the Western 

 Atlantic. They must however to some extent be due to the 

 unusually warm winter which seems to have prevailed pretty 

 uniformly over the North Atlantic and North- West Europe, and 

 which has detached a larger proportion than usual of the Arctic 

 ice-fields. And though it is improbable that we shall find any 

 such regular periodicity in the amount of these ice-floes in the 

 Atlantic as in that of the Indian winter snows and rains, it is 

 worthy of notice to observe that they have a decided tendency to 

 occur to an uuuonted extent about the times of maximum sun- 

 spot — like the present. Thus Prof. Fritz, of Zurich, 1 gives the 

 following as the list of years in which floating ice was found 

 most abundantly in the lower latitudes of the North Atlantic : — 



Years of greatest frequency Epochs of maximum 



of floating ice. sun-spot. 



I7S9 I7SST 



1S042 

 l8l6-l8 1816-4 



I82S-2Q. ) o 



.831 i i82 " 



1837-2 



1848-1 



1862-64 18601 



l86S I ,8,,,-fi 



1869 i l8 7° 6 



It is also interesting to notice that in 1862 Heis's " Wochen- 

 schrift" mentions that the floating ice-masses in the Atlantic caused 

 "a noticeable cooling of the weather in June over Europe." 

 And it is further significant to find in a detailed list of the ice met 

 with every month in the Atlantic by ships belonging to the North 

 German lines from 1S60 to 1S69, that 1S6S and 1S69 (the year in 

 which similar weather to the present is mentioned as having been 

 observed by the writer of the paragraph in Nature) were the 

 years in which the greatest quantity of ice was encountered. 

 Though I agree with Dr. Hann in attributing more importance 

 to the tropical than to the polar area, in influencing the general 

 weather of these latitudes, I think it very probable on theoretical 

 grounds that we are relatively more influenced by the latter 

 area in summer and by the former in winter, and that just as it 

 has been inferred that the regular recurrence of periods of 

 diminished temperature in Europe, is due to the regular move- 

 ments of the ice in the polar area so we may reasonably conclude 

 that abnormal movements of the ice, especially in the Spitzbergen 

 area, are likely to produce periods of abnormal coolness such as 

 that which at present prevails. In any case the moral to be 

 drawn, if we redly do intend to solve the weather problem, is by 

 all means to have a meteorological station in Iceland, and 

 endeavour to study the weather as we are fortunately able to do 

 in India, on a large scale, instead of merely confining our attention 

 to the minute range of conditions we are able to observe within 

 the limited area of these islands. 



E. Douglas Archibald 



The Analysis of the Tuning Fork 

 In Nature last week there is a short description of Mr. 

 W. F. Stanley's well-devised experiments, by which the tuning- 

 fork " is shown not to depend upon a vibrating ventroid." 



Few persons would readily obtain the experimental steel rod, 

 or would care to attempt the feat of sawing through the bend of 

 the fork down into the stem, and some musical readers may like 

 to know that (missing, of course, the pretty effects) there is a less 

 arduous way of arriving at the conclusion to which Mr. Stanley 

 has directed attention. By very simple experiments I have been 

 accustomed to show that Chladai's analysis, as generally accepted, 



1 In his work, " Ueber die Beziehunjen der Sonnen flecken-periode zn den 

 Meteocologischen unt Magnetischen Erscheinungen," p. 175. 



is not in all particulars borne out by the evidence of facts. If a 

 vibrating tuning fork is held in its upright position by means of 

 a knife-blade passed through the prongs, pressing upon the inner 

 bend so that the stem is in contact with the table, without its 

 being held by the fingers, there will be a communication of vibra- 

 tions fully as strong as when held in the usual manner, with 

 variation of intensities according to differences in the degrees of 

 pressure. In this experiment the fork at its bend is subjected to 

 pressure both above and below. The argument, therefore, is 

 that the existence of a segment in transversal vibration, occupy- 

 ing the bend of the fork as figured in Chladni's analysis, is in- 

 compatible with the evidence. As in all musical instruments, 

 the communicating of transversal vibrations from one solid to 

 another is invariably through the nodes, and as segments are 

 always destroyed by firm pressure, it seems clear that the 

 analysis should be amended. If a vibrating fork is drawn across 

 a stretched string with pressure, the prong passing from the bend 

 towards the point or end, the integrity of the vibrations of the 

 fork is not impaired, and there is but a slight transference of 

 vibration to the siring ; but it is otherwise with respect to a 

 stretched wire, as when the prong comes into contact with the 

 wire, its vibrations cease ; the wire will not be subordinated to 

 the coercive activity of the prong as the string is ; yet if the fork 

 is placed with the prongs astride the wire, so that the bend, at 

 the seat of the alleged segment, rides upon the wire, the wire 

 readily conveys the vibrations, and acts as a sound-post. It may 

 be shown that the stem of the fork acts likewise as a sound-post, 

 since we may substitute a free stem ; if a vibrating fork is held 

 by the stem, and if through the prongs another fork has the 

 shoulder of its stem pressed upon the bend, then, when the point 

 of this second stem is brought into contact with a solid, the 

 vibrations of the fork are transmitted through it from the bend, 

 with nearly the strength of tone as would be produced by the 

 original fixed stem. The stem itself may be dispensed with as 

 a part of the system, for if the fork is held so that the external 

 part of the bend, where it joins the stem, is pressed against the 

 edge of a table or other solid, its vibrations are not interfered 

 with ; neither is the strength of tone diminished, except as in 

 each of these instances, varying in the usual way according to 

 the degree of pressure. Hermann Smith 



June 19 



"Combing" of Waves 



All who have watched waves breaking on the sea-shore must 

 have noticed the furrowed or "combed " appearance of the back 

 of a wave as it curls over. If the water is not much disturbed 

 by wind, it is seen, on attentive watching, that this "combing" 

 appears suddenly, and begins at the advancing edge of the crest, 

 and spreads backwards. With small waves a foot or so in height 

 and of long extended front, such as are seen in shallow water, it 

 may be observed that the crest, which in this case rolls down the 

 front of the wave, is at first smooth and even, while the back of 

 the wave is also smooth and unfurrowed, but the edge of the 

 crest suddenly becomes crenated, and almost simultaneously the 

 combing appears on the back of the wave, travelling rapidly 

 backwards from the crenated edge. Moreover a considerable 

 length of the wave appears to be similarly affected almost at the 

 same instant. With larger waves, whose crest falls rather than 

 rolls upon the concave front, I have observed that the edge is at 

 first smooth and even, but that it suddenly becomes uneven, and 

 often fringed with a row or rows of drops, and that at the same 

 instant the combing appears. In both cases, if there is much wind, 

 the regularity of the phenomenon is di-turbed, and observation is 

 in other ways rendered difficult. The action is so exactly parallel 

 to something which takes place in the splash of drops, and which I 

 have described in detail in a paper recently read before the Royal 

 Society (see Proc.' Roy. Sue., No. 21S), that I think your 

 readers may be interested in a brief statement, with special 

 reference to this more familiar case of waves, of the explanation 

 there put forward. The explanation amounts to this : — It is 

 well known that a long cylinder of liquid is unstable, and will, 

 if left to itself, at once tend to split into a row of equal, equi- 

 distant drops ; the splitting being effected by a constriction of 

 the cylinder in certain places, and a bulging out in others. 

 Again, if a mass of liquid is bounded by an edge whose surface 

 is approximately a portion. of a long cylinder, there is good 

 reason for supposing that this cylindrical edge will be subject to 

 similar laws of stability, and that it will tend to cleave in the 

 same way, the surface being forced in in certain places, and out 

 in others. Now a wave's crest presents such a cylindrical edge. 



