38S 



NATURE 



[August i8, 1892 



Profe-isor Cer'ruti, on behalf of the second committee, reported 

 that two candidates had been found equally deserving of the 

 mathematical prize, viz.. Professor Luigi Bianchi by his essays 

 on the triple orthogonal systems of Weingarten and allied sub- 

 jects, and Professor Salvatore Pincherle in virtue of his various 

 wrorks on the general theory of functions. It was therefore 

 decided to divide the prize equally among these two candidates. 

 — The last of the ministerial prizes for professors of secondary 

 classical and technical schools, amounting to a total of 9000 lire 

 for philological, and 9000 lire for physical and chemical 

 subjects, were distributed among thirteen candidates, prizes of 

 3000 lire being obtained by Professors Nasini and Costa for 

 their work " On the Variation of Refractive and Dispersive 

 Power of Sulphur in its Compounds," and by Dr. Enrico 

 Salvioni for his contribution "On the Construction of the Legal 

 Ohm." — General Ferrero then addressed the meeting on the 

 subject of scientific measuring instruments. Although, he said, 

 the human eye, that natural model of the telescope, the micro- 

 scope, and the photographic camera, can distinguish within a 

 few hundredths of a millimetre whether two points are in con- 

 tact ; although the ear can appreciate sounds ranging from 32 

 to 70,000 vibrations per second, and is able, while following the 

 rhythm of a full orchestra, to discover the slightest dissonance ; 

 yet the power of our senses is limited to a comparatively small 

 portion of the infinite variety • of external phenomena, that 

 portion which is of more immediate value for our merely animal 

 life. The errors which the unaided senses are liable to lead us 

 into are mainly due to their subjectivity, which renders the 

 impressions of one individual incomparable with those of 

 another, or with his own under different conditions. The use 

 of instruments enables us to submit these impressions to 

 measurement, to compare them amongst themselves, and 

 immensely to extend our field of investigation towards the 

 infinitely great and the infinitely small. The progress made in 

 this direction during the last few hundred years justifies the 

 hope that the time is not far distant when the results of observa- 

 tion will be as far as possible beyond the personal influence of 

 the observer. The disciple of science will read the truth in the 

 book of nature, traced out by the phenomena themselves. The 

 universe, which has always remained inaccessible to metaphysics, 

 will willingly disclose its secrets to the researches of modern 

 science. This owes its great progress during the last century 

 mainly to the perfection and delicacy of its measuring instru- 

 ments, which has made modern astronomical observations a 

 thousand times more accurate than those of the Chaldees, and 

 has, by making very minute differences of temperature appreci- 

 able and measurable, enabled biology to enter the ranks of the 

 exact sciences. The accuracy of measurements of length and 

 mass is ensured by the arrangements in connection with the 

 International Office of Weights and Measures at Breteuil. Some 

 recent comparisons of standards gave a probable error in length 

 of 1/20, 000mm., while that for mass was 4/10CO mgr. The 

 determination of weight has been carried to such a pitch of 

 accuracy, that it has been found possible, at Breteuil, at 

 Monaco, and at Rome, to measure the slight differences of 

 weight produced by varying the height above the ground by a 

 few metres. For the measurement of time there has been no 

 necessity of fixing a conventional standard. The marvellous 

 invention of the pendulum has made it possible to subdivide 

 almost indefinitely the natural fundamental unit, the duration of 

 the rotation of the earth. In the determination of longitudes 

 the error has been reduced to one or two hundredths of a second. 

 Hipp's chronoscope, which may be called a microscope for time, 

 enables the observer to subdivide time to a thousandth of a 

 second. The impulse given to biological research by such in- 

 struments has been astonishing. The time of reaction to the 

 various sensory stimuli has been fixed at 136 thousandths of a 

 second for sound, at 150 for light, 133 for touch, 359 for taste, 

 and 443 for smell, while the velocity of propagation of a nervous 

 impulse has shown itself to be 37m. per second. In artillery, 

 the chronoscope has been utilized for the study of the initial 

 •velocities of projectiles, and for the tracing of diagrams express- 

 ing the relations between spaces, times, and explosive pressures. 

 Errors of observation may be due to the imperfection of the 

 senses, to unavoidable faults in the construction of the instru- 

 ments, and to external influences. These may be classified 

 according as they are constant or accidental, or better as 

 periodical or otherwise. Most of the errors due to the observer, 

 and of those due to external influences, are periodical, and may 



be eliminated by repeating the observations under varying con- 

 ditions. The calculus of probabilities shows that the precision 

 of results, so far as the elimination of purely accidental errors is 

 concerned, increases with the square root of the number of 

 observations. But experience shows that beyond a certain 

 number of observations the increase of precision is illusory. 

 This is probably due to the existence of other errors of a constant 

 character which escape analysis, and from which it is not possi- 

 ble to protect the observations. Experiment also proves that for 

 all kinds of work the maximum error does not exceed a certain 

 limit, which is a function of the mean error. For angular 

 measurements, this does not exceed three times the mean error, 

 so that according to Gauss's law of errors it would be safe to 

 lay 1000 to I against the chance of an error greater than 3*2 

 times the mean error. The observer himself must above all 

 have physical qualities enabling him to use his senses under the 

 best possible conditions. In addition to well-trained senses and 

 facility in managing his instrument, he must have a clear mind, 

 a correct judgment, and a sound scientific preparation for the 

 research he undertakes. Concentrated upon his research, he 

 must abstract himself from the surroundings among which he 

 lives, and possess a spirit unimpassioned enough to subject him- 

 self to a purely objective criticism. In concluding, the speaker 

 pointed out that there is at present no science which treats of 

 measurement in general, as a preparation to all the sciences 

 which aim at quantitative results. Many treatises on astronomy, 

 on geodesy, on physics are prefaced by theories of instruments 

 and the compensation of errors. But even those works which 

 profess to treat of the art of measuring are usually limited to 

 geodetic and topographic measurements. It is to be hoped that 

 this important vacancy may soon be filled up, and that a Science 

 of Measiirevient will unite the elements dispersed among the 

 various sciences in one compact and harmonious whole. 



CONTENTS. PAGE 



A Debatable Land— Plants or Animals? 365 



Letters to the Editor :— 



The Apodidse— a Reply. —Henry M. Bernard . . 366 

 Calculation of Trajectories of Elongated Projectiles.— 



Rev. F. Bashforth 366 



A Plea for an International Zoological Record.— E. . 



A. Minchin 3^7 



Pilchards and Blue Sharks.— Matthias Dunn ... 368 

 Aurora Borealis.— A. Butcher; Rev. Edmund 



McClure ; J. Lloyd Bozward . , 368 



Aurora Australis.— William White; H. S. Dove 



and G. W. Easton 368 



Units Discussion at British Association. — Prof. 



Oliver J. Lodge, F.R.S 368 



The Varley Testimonial 3^9 



Notes 369 



Our Astronomical Column : — 



The Perseids 37i 



" Himmel und Erde " 37^ 



Astronomy at the Columbian Exposition ...... 37 2 



Lunar Eclipse, May II, 1892 372 



Numeration of Asteroids . 37^ 



The British Association : — 



Section C— Geology.— Opening Address by Prof. 

 C. Lapworth, LL.D., F.R.S., F.G.S., Presi- 

 dent of the Section 372 



Section H— Anthropology.— Opening Address by 

 Alexander Macalister, M.D., F.R.S., Professor 

 of Anatomy in the University of Cambridge, Presi- 

 dent of the Section 378 



Physics at the British Association 382 



The Periodic Variations of Alpine Glaciers: By F, 



A. Forel 386' 



Societies and Academies 387 



NO. 



II 90, VOL. 46] 



