146 



NATURE 



\yune 24, 1875 



fi cation of a philosopher's misapprehension, and is meant to show- 

 not only that an organ-pipe behaves itself in a manner different to 

 that with which it is accredited, but also why it does so ; to show 

 ho\v important a matter in the nature of its action is this neglected 

 difference, and how wide its bearing on the whole system of mu- 

 sical instruments. Here at my hand is a stopped pipe sounding 

 mid C. I measure it interiorly from languid to stopper ; it is 

 eleven inches in length, and has a diameter of one-and-a-half 

 inches. Here is an open pipe, same pitch, same diameter, and 

 its length is twenty-three inches. Observe, our stopped pipe is 

 half an inch less in length than half that of the open pipe ; yet 

 again notice, it is longer than that pipe would be if severed at 

 the trae nodal distance from the languid. How can we read 

 eleven as precisely thirteen, and twenty-three as twenty-six 

 inches ? Under the strange notion that it is no matter if there 

 is a difference, this has been done, and the truth of facts lost 

 sight of or disguised in the convenient phrase, "approximately 

 correct." The phrase assumes that there is a standard claiming 

 nature's allegiance. We want to know, not what is correct, but 

 what is true ? Further, remark that if you stop the same open 

 pipe at the top, the note obtained will not be an octave deeper, 

 it will be nearly a tone sharper than that ; if you stop the pipe 

 at the centre, the note will not be the same as the open one, it 

 will be considerably flatter ; in neither case a good tone, since 

 for its proper sounding in such condition the lip would require 

 to be cut higher, mouth a little narrower, perhaps curved, and 

 languid lowered. Every detail we come upon tells plainly of 

 the working power of the reed affecting variably the results in 

 pitch, and I think the reason for these distinctive sounding 

 lengths will be discerned when we reach the consideration of 

 the question of 'periods of vibration in pipes as tempered by 

 rests. 



The fundamental importance of the recognition that pipes of 

 the same pitch varied between themselves as to lengths, was not 

 perceived, nevertheless a qualifying condition was admitted that 

 pitch was " affected by a'l?//// of the pipe, that is, its distance 

 from front to back, but width does not affect pitch. " As regards 

 " depth, "rin no work whhin my knowledge does there exist any 

 attempt at a solution of the problem how such a result ensues 

 that depth interferes with pitch. It seems to be taken account 

 of only as a disturber of the harmony of things, yet see how sig- 

 nificant it is under the new theory of the working abstracting 

 reed. The actual law operating admits of most precise state- 

 ment when this generating power is acknowledged, viz., the 

 difference of pitch in pipes of varied diameter (other things being 

 equal) is proportional to the difference existing between the area 

 of the cross- section of the pipe and the area of the mouth ; the 

 difference in pitch is greatest when the depth from front to back 

 is greatest. It should be observed that increase of depth always 

 flattens pitch, and tends to deprive the pipe of harmonic force. 

 As regards the further assertion that "width" is without effect 

 on pitch, this also is inexact and misses the very point which 

 should have led to closer investigation. It is not true, because 

 the same amount of wind acting over a wider area cannot do the 

 larger extent of work with the same energy. The pitch of every 

 pipe is affected by the width of mouth 7-elatively, that is to say, 

 its proportion to the diameter of the pipe. Apart from the 

 ordinary rectangular and cylindrical pipes there are others of so- 

 called "irregular shapes," which are' usually viewed as monstro- 

 sities, out of the pale even of law padded with exceptions ; yet 

 these we shall find are the best evidence to us of the uniformity 

 of the principle of action set forth in these papers, and of the 

 consistency of a theory which recognises no exceptions. 



Cylindrical pipes, notwithstanding their symmetry, differ 

 greatly among themselves. The law by which flue-pipes differ 

 has never yet been noticed, which is singular, since it is very 

 striking when the pipes are thoughtfully observed, and gave the 

 first clue to the theory of an areo-plastic reed. A student well 

 read in all that the best text-books in acoustics can teach, coming 

 to the practical study of organ-pipes, and seeing in a grand 

 organ so multitudinous an array of pipes, the unison pipes of the 

 several stops conspicuous for diversities of diameter as well as 

 of length, would naturally expect that here, if anywhere, he 

 would find confirmation of Reynault's law, "The velocity of 

 propagation of a wave of the sam.e intensity in straight lines 

 is less according as the section of the tube is less." No ! this 

 small comfort is denied him ; he is in a world of contrarieties; the 

 law is abrogated ; he will find the organ world de facto governed 

 on prmciples the exact opposite, " llie velocity is greater as the 

 section ts less." Investigating further, he will find that, although 

 in length the octaves of particular flue-stops^ examined are each 



very closely upon half the length of the other, yet their diame- 

 ters do not follow a similar rule, for instead of octave or double 

 octave being in that ratio, he must from the pitch note count to 

 the seventeenth pipe before he will arrive at a pipe half its 

 diameter. For other seeming anomalies, let him proceed to the 

 stops called bassoon, trumpet, and tuba, and he will find that 

 here increase of diameter demands not less length, but greatly 

 increased length, to accompany increase of scale. Books of 

 latest authorities will tell him that in an organ-pipe with a 

 metallic reed "the note produced depends upon the length of 

 the pipe rather than upon the length of the reed. In fact, when 

 the note is established the reed obeys the impulses it receives 

 from the air in the tube. Its use is accordingly rather to econo- 

 mise air and to give certamty and percussion to the striking of 

 the note." Alas, it is inference by theory without test. Remove 

 the whole of the eight or nine feet of the tube, leaving but the 

 few inches of cup or socket, _and you will have altered the pitch 

 not more than a semitone. 



All organ -pipes having metallic reeds act in conformity with 

 Regnault's law, and the same holds good of wind instruments- 

 trumpets, bassoons, and the like. All organ-pipes possessing 

 air-reeds, flutes also, and some whistles, not all, display an 

 opposite law. The musical tones of all in both these systems 

 are the result of " suction by velocity," and the distinction is that 

 in the former the intermittence is produced by suction under a 

 propulsive current, and in the latter by suction under an abstracting 

 current. The fact announces the law and leads to its explanation. 



Hermann Smith 



Faults and the Features of the Earth 



My attention has been drawn to an article in Nature, vol. xii. 

 p. 93, on an exploring party of the Geological Class of the 

 University of Edinburgh to trace out a long fault in Scotland. 

 In this it is stated that particular attention was devoted by the 

 party to the connection between dislocations and valleys, and 

 tbey came to the conclusion that not a single main valley ran 

 along the fault they were tracing out. As an advocate of the 

 theory that faults or other breaks greatly induced the present fea- 

 tures of the earth, perhaps you may allow me to say a few words 

 on the subject. 



Fault-rock may be friable or hard ; the first is inclined to 

 induce valleys, the second peaks or ridges. Faults are of 

 different ages, and therefore the features due to them are liable 

 to be obliterated. Pre-Silurian features may be obliterated by 

 the subsequent deposition of Silurian rocks, and so on upwards 

 until we find many preglacial features obliterated by the glacial 

 drift. In Ireland and Scotland we find more faults in the meta- 

 morphic rocks than in the overlying Silurians, in the Silurians 

 than in the overlying Carboniferous and Old Red Sandstone, and 

 in the Carbonilerous than in the drift, while each newer accumu- 

 lation obhterated, or perhaps, more properly, obscured the 

 features in the older. 



The fault examined by this party, from the brief description, 

 seems, first, to have had a hard fault-rock, and second, its age 

 to have been far from recent. Consequently, by the first, if the 

 fault induced any features at all in the present surface, they 

 ought to have been peaks or a ridge like that formed by the 

 great Slieve-muck fault in Tipperary, Ireland ; while if the second 

 is correct, this fault ought not to form surface features, as any 

 features due to the original fault were long since obliterated ; 

 also, the fault has been cut up and displaced by the more recent 

 movements. If a valley chances to run along the line of an 

 ancient fault, it probably was not induced by that fault, but by a 

 much more recent break that for a greater or less distance coin- 

 cided with the line of the older fault. G. H. KiNAHAN 



Wexford, June 18 



Salaries in the British Museum 

 Among your notes of last week is a favourable announcement 

 of my promotion as an assistant in the Geological Department 

 of the British Museum ; but whilst thanking you, allow me to 

 point out that it contains a grave misstatement as to the amount 

 of remuneration I receive for my services (as a reference to the 

 Parliamentary Returns will demonstrate) ; a misstatement alike 

 unjust to the trustees and to myself. 



May I venture to ask you to insert this, and so correct the 

 erroneous impression which the paragraph conveys, as to the 

 small amount of the pay received by myself and others in a 

 similar position on the establishment. 



British Museum, June 15 Wm. Davies 



