June 24, 1875] 



NATURE 



145 



found in the chapters on electro-metallurgy, a subject 

 that is discussed with great detail, too much so, however, 

 for a general treatise. The author has evidently been at 

 no little pains to collect the numerous tables he gives, 

 and in some instances they are the results of his own 

 experiments. There is also a freshness and originality in 

 the treatment of the sections on resistance and electro- 

 motive force that make us regret Mr. Sprague did not 

 submit his theoretical views to some scientific friend 

 before sending his work to the press. If the author had 

 confined himself to the practical part of current electricity 

 we should gladly have recommended his book to our 

 readers. 



OUR BOOK SHELF 



Anales del Museo Publico de Btienos Ayres para dar a 

 conocer los objetos de Hisioria A atural nuevos o poco 

 conocidos conservados en este establecimento. Por 

 German Burmeister, M.D., vol. ii. (Buenos Ayres and 

 London : Taylor and Francis.) 

 In previous numbers of Nature (vol. iii. p. 282, and 

 vol. vii. p. 240), we have given some account of the im- 

 portant work which the well-known German naturalist, 

 Dr. Burmeister, is now carrying on at Buenos Ayres. 



The number of the Anales now before us completes the 

 second volume of this remarkable work, and gives us 

 additional proof of the extraordinary richness of the 

 extinct Mammalian Fauna of the Argentine Republic, to 

 which Dr. Burmeister has devoted so much attention. 

 The Monograph of the Glyptodonts, or extinct gigantic 

 fossil Armadillos, which is raw brought to a conclusion, 

 is certainly one of the most valuable contributions to 

 palaeontological science that has been produced of late 

 years, and deserves the hearty commendation of all natu- 

 ralists. This is more especially the case when we con- 

 sider the difficulties under which the work has been 

 carried on — in a new country, where every man avidus lucri 

 is striving to advance his own material interests, and sci- 

 ence and all that pertains to it are at an utter discount. On 

 one occasion , we have been told, when one of the most per- 

 fect of these Glyptodont skeletons came into the market, the 

 authorities of the National Museum were unwilling or un- 

 able to raise the necessary funds to secure it, and it would 

 have left the country and been lost to Dr. Burmeister 

 and his Monograph, had not an English friend found the 

 money. Then, again, the necessity of having the plates 

 lithographed in Europe must add greatly to the difficulties 

 of the undertaking. Under these circumstances we may 

 fairly congratulate Dr. Burmeister and science on the 

 occasion of the second volume of the Annals of the 

 Public Museum of Buenos Ayres having been brought to 

 a successful conclusion. 



LETTERS TO THE EDITOR 

 \l^he Editor does not hold himself responsible for opinions expressed 

 ^gjlrc by his correspondents. Neither can he undertake to return, 

 or to correspond with the writers of, rejected manuscripts, 

 No notice is taken of anonymous communications.] 



Peculiarities of Stopped Pipes, Humming-tops, and 

 other Varieties of Organ-pipes 



The peculiarities of a stopped organ-pipe as compared with 

 an open organ-pipe are many and suggestive, and are of the 

 utmost importance to the investigator both to know and to 

 interpret. W'ithcut entering deeply into the principles of the 

 craft of organ-building, there are certain matters of lact very 

 necessary to be known before the full bearing of a theory can be 

 estimated or its consistency be judged with true understanding. 



By far the greater portion of an organ consists of pipes of the 

 s nicture called "flue-pipes," or, as here named, "air-reed" 



pipes, and thes^ are of two classes, the open and the stopped ; 

 also they are of two kinds, wood and metal. We have to notice 

 how differently these two kinds are constructed to attain the same 

 ends. In the metal pipe every part is to all appearance immove- 

 able. In the wooden pipe the under-lip, or technically the 

 "cap," is the only adjustable part, end is fixed in position by 

 two or more screws. Within the mouth there is a platform 

 filling the space beyond the windway ; it is called the " languid," 

 and it is by varying relatively the level of the edge of the cap to 

 the edge of the languid that the direction of the stream of air is 

 determined ; if the cap is set low the angle of flow outward is 

 increased, contrariwise it is lessened, and the art of the voicer 

 decides to the finest degree what is requisite for the quality and 

 speech of each particular pipe. If the wind is much thrown 

 outwards, the speech is slow ; if more inward, the speech is 

 quickened ; if too much inward, the octave sounds instead of 

 the ground-tone ; if too much outward or inward, the pipe will 

 not speak at all. One more power of adjustment remains — the 

 width of the narrow slit through which the wind issues is 

 capable of being varied by alteration of the inner surface of 

 the cap ; a wide windway gives a stiffer air-reed, a fine windway 

 gives a thinner one. In a metal pipe we have precisely the 

 same capability of variation, only that we effect our purpose by 

 pressure; the languid is moved higher or lower, not the cap. 

 By means of a rod introduced at the foot or at the top of the 

 pipe, we tap or press the languid into the desired relation to the 

 edge of the underlip. We can also press the upper lip forward 

 or backward ; we can, by a like process, reduce the windway or 

 enlarge it as easily. Very simple, yet very beautiful, compensa- 

 tions. In the variations of construction, nothing is done without 

 purpose, nor can you make any one of these minute changes 

 without causing at the fame time a flattening or sharpening of 

 the pitch, or a diversity in intonation or quality. 



The above details all tend to one point, which I wish to press 

 upon your attention ; one distinctive feature belongs to the 

 stopped pipe : the languid is lower than in an open pipe, else 

 the pipe does not attain its proper speech. Consider ii: well, for 

 it is a fact full of meaning. A necessity of an opposite kind exists 

 in the nature of an open pipe ; its demand is that the current 

 f.hall have determination more to an outward flow. The cause 

 of so essential a distinction between the two classes of pipes will 

 be explained in another paper. 



Stopped pipes when they are deep-toned are called "Bour- 

 dons," the name the French give to the Humble Bee for its 

 " drowsy hum." Our plaything, " the humming-top," is a true 

 bourdon, is a revolving organ-pipe, has a vibrating air-reed, its 

 principle of action is "suction by velocity," the abstraction of 

 air particles by velocity of rotation causing a partial vacuum just 

 as in the stationary organ-pipe by velocity q{ passage of a current 

 of wind. 



Bearing in mind the working power of the air-reed, we are 

 brought to consider the effects of the dimensions of the pipe 

 and consequently of the form as well as the extent of the air- 

 column whereon this power is impelled to act, and it is neces- 

 sary to recur in passing to the question of length. Scientific 

 writers affirm that the length of an organ-pipe for a given note 

 corresponds to the length of the wave in air with an absolute 

 relation, thus expressed. Prof. Tyndall says : " The length of a 

 stopped pipe is one-fourth that of the sonorous wave which it 

 produces, whilst the length of an open pipe is one-half that of 

 the sonorous wave." Prof. Balfour Stewart says, in his "Ele- 

 mentary Lessons in Physics" : " In an organ-pipe of this kind, 

 the upper end closed, the primary note is that of which the wave 

 length is twice the length of the pipe ... the wave length of 

 the sound produced by an open pipe is equal to the length of the 

 pipe, so that it is only half of that produced by a shut pipe of 

 the same length." (One is curious to know why there is this 

 difference of statement from two leading teachers of men ; per- 

 plexing to the student in want of a leader). Prof. Tyndall 

 demonstrates his affirmation, showing that a stopped tube re- 

 sounds to the note mid C of 256 vibrations per second ; the wave 

 length in air of this note he states to be fifty-two inches ; then in 

 proof he measures the jar or tube, and says, " by measurement 

 with a two-foot rule I find it to be thirteen inches, precisely a 

 fourth of the wave length." He then proceeds to affirm the same 

 of organ-pipes, and proves it by tuning-forks and by sounding 

 the pipes to the same note, and believes he has justified his asser- 

 tions. His hearers do him that justice, and go home believing 

 also. The proof is, however, altogether illusive. No speaking 

 organ-pipe of that length ever gave the note of that pitch. Let 

 us put the assertion to^he test. My object hes beyond the recti- 



