ISO 



NATURE 



[April 13, 1916 



INSTRUMENTAL HARMONIC SYNTHESIS. 



'T*HE Journal of the Franklin Institute for January 

 •■■ contains a detailed description by Prof. Dayton C. 

 Miller of a "32-element harmonic synthesizer" (would 

 not synthetiser be more euphonious?), which appears 

 to be admirably designed for many purposes. The 

 main intention is to test the accuracy of any given 

 harmonic analysis by recombining the harmonic 

 terms and comparing the curve so obtained by syn- 

 thesis with the original form analysed. 



The principles of construction of the instrument are 

 the same as those exemplified in Kelvin's tide pre- 

 dicter, but the investigations iq photogfaphic records 

 of sounds for which the instrument was devised led to 

 important differences in detail. For example, instead 

 of a metallic ribbon threading the pulleys connected 

 with the elements, a flexible chain of the chronometer 

 fusee type is used. One end of this chain is attached 

 to the pen-carriage above the drawing board on which 

 the record is produced ; the other end supports a 

 weight, and the chain is clamped at a convenient 

 intermediate point to a bar which passes under the 

 chain as it crosses and recrosses from pulley to pulley. 

 If the clamp is set at the far end' of this rod, all the 

 32 elements influence the motion of the recording pen. 

 If, hov.'ever, the higher elements are not to be used, the 



Fig. I. — Pioof of the analysis of a curve by synthssis. 



clamp is shifted nearer to the drawing-board, and the 

 pen is not influenced by^ the movements of these higher 

 elements. The elements are arranged upon a table 

 with their shafts vertical, and are geared together in 

 such a way that when a handle is turned the rates 

 of rotation of the successive elements are as the 

 numbers i, 2, 3, 4, etc., up to 32. 



The satisfactory action of the instrument is well 

 shown in a figure in which the synthetic reproduction 

 of the analysis of the curve of an organ-pipe note is 

 superposed upon an enlarged photograph of the original 

 (Fig. i). There is perfect coincidence. Another figure 

 illustrates the sound wave from a clarinet and gives 

 the harmonic components to the 29th term. Particu- 

 larly interesting also are the representative curves built 

 up of 15 or 30 terms of certain well-known Fourier 

 series, which when summed to infinity give har- 

 monic forms composed of straight lines. Beautiful 

 examples are also given of beats obtained by the com- 

 bination of two harmonic forms the frequencies of 

 which are in the ratio of 10 : 29, 15 : 29, and 29 : 30. It 

 should be mentioned that the instrument was origin- 

 ally designed to be used in connection with Henrici's 

 analyser, which requires that all curves for analysis 

 be drawn with a wave-length of 400 millimetres. 



NO. 2424, VOL. 97] 



CEMENTS AND CLAYS. 



'"PHE Bureau of Standards (U.S. Department of 

 ^ Commerce) issues from time to time Technologic 

 Papers bearing on various subjects of practical im- 

 portance. Several of these papers dealing with 

 cements and related subjects are before us. 



No. 47 of the recent pamphlets deals with "The 

 High-Pressure Steam Test of Portland Cements," and 

 it is inferred from the results of the official investiga- 

 tion that the value of this rapid test varies greatly 

 with the conditions (especially when abnormal) under 

 which the material is to be employed. No. 48 describes 

 a new "Air Analyser for Determining the Fineness 

 of Cement." The chief distinguishing feature of this 

 new elutriator is the principle of blowing an un- 

 retarded stream of air down into the cement from 

 above, the sample being completely and continuously 

 exposed in a conical bulb to the action of the air. 

 It has been found to be well adapted for separations 

 of various hard-grained materials, and might prove 

 useful in other directions. 



No. 51 refers to "The Use of Sodium Salts In the 

 Purification of Clays and in the Casting Process." It 

 is of special interest to those who are engaged in the 

 ceramic industries, and in the working of clav de- 

 posits, but, being largely concerned with phenomena 

 depending on viscosity, it may appeal to a wiier 

 circle. From results of experiments it is inferred that 

 the German electrical osmosis process plays no im- 

 portant part in the actual purification of clavs, bat 

 facilitates the deposition of the suspended particles on 

 the electrode. The essential feature of the osmosis 

 process appears to be the preliminary sedimentation pro- 

 cess, in which a small proportion of caustic soda or 

 other electrolyte is added to the clay mixed with water, 

 and after well stirring, the coarser material is removed 

 by means of screens and settling. During the inves- 

 tigation a new efflux viscosimeter of simple construc- 

 tion was devised, consisting of a brass tube with 

 appropriate fittings. This inexpensive instrument is 

 stated to be sufficiently accurate for purposes of com- 

 parison, the kinetic and temperature corrections 

 applied in precise measurements not being necessary 

 for technical work. Possibly the instrument (or some 

 modification of it) might find useful application m 

 connection with other technical processes where vis- 

 cosity is an important factor. J. A. A. 



PRODUCTIVE RESEARCH IN THE 

 UNITED STATES?- 



THAT the scientific method, which furnishes the 

 instruments and the criteria for effective investi- 

 gation, is now gaining esteem with unreflective as 

 well as with reflective . minds is in evidence in 

 nearly every field of current activity. In the report 

 for the year 1914 attention was directed to the rise of 

 other research establishments and to the relations of 

 reciprocity the institution should sustain to them. 

 Several of these have effected organisation during the 

 past year, and more such are in process of develop- 

 ment. 



Simultaneously with the rise of other research 

 organisations, the scientific method is rapidly gaining 

 control in the direction of commercial and industrial 

 enterprises. Indeed, the phrases " scientific manage- 

 ment," " industrial efficiency," and the like, are now 

 so much over-applied and so often misapplied as to 

 render them offensive to judicially conservative mindsj 

 for herein likewise, as in most other contemporar 

 affairs, there is a popular tendency to anticipate tr 



1 Abridged from the Report of the I'resident of the Carnegie Institutio 

 of Washington contained in Year Book No. 14, 1915. 



