August 29, 19 18] 



NATURE 



5^7 



— have been under investigation. So, too, have 

 :)een the low vakies of available potash in certain i 

 other soils. In this connection efforts have been j 

 made not only to correlate potash-deficiency with , 

 disease in -animals and plants, but also to utilise ' 

 the ash of at least one proclaimed weed as a 1 

 means of adding potash to the soil, and inci- ! 

 dentally as a partial set-off against the cost of j 

 erajdication. Botanical work has included, in ' 

 addition to survey operations, much that is of j 

 immediate economic importance. One notable ,, 

 instance is afforded by the device of a method of 1 

 selfing cotton, which is not only simple, but is 

 also said to have proved successful. Much sound i 



work has been done with indigo, jute, opium, 

 rice, sugar, and wheat on agricultural lines, and 

 with grasses, as well as trees, on forestry lines. 



On the physical side we find that researches 

 in solar physics have included an investigation of 

 the displacement of the lines of the solar spectrum 

 compared with lines given by the electric arc. 

 This study has supplied interesting results, and 

 led further to a determination of wave-lengths 

 in the spectrum of the planet Venus with results 

 that are of promise. In geology, besides survey 

 operations, useful economic work has been done 

 in connection with the output of wolfram. Three 

 new meteorite falls — all chondrites — have been re- 

 ported for 1916-17 from northern India. The 

 most notable item of economic geodetic work for 

 the year has been the taking of hourly readings 

 of a tide-gauge at Basra, erected in connection 

 with military requirements. The constants de- 

 duced from the reductions of these readings have 

 been transmitted to the National Physical Labora- 

 tory at Teddington, to admit of the tracing of 

 tidal curves for 1917-18. Important also has 

 been the compilation of a list of the plumb-line 

 deflection stations of India and Burma. 



The work undertaken in connection with plant- 

 and animal-pathology has been useful and 

 varied. In this relationship an item which 

 deserves attention is an account of practical 

 tests of the use of hydrocyanic acid gas for the 

 destruction of vermin. While less successful than 

 might be desired in the case of houses, this 

 method has proved satisfactory as regards rail- 

 way carriages and ships. 



Appended to the report is a memorandum on 

 work done for India at the Imperial Institute. 

 A striking item in this memorandum is the record 

 of a sample of Assam-grown flax, valued in Lon- 

 don under war conditions in December, 1916, at 

 150Z, per ton, which was found to compare favour- 

 ably with the medium qualities formerly received 

 from Belgium. 



Perhaps the time is approaching when a body, 

 similar in its functions to this Indian board, may 

 be brought into being so as to ensure for the 

 scientific departments of our various Crown 

 Colonies that correlation of effort which, as this 

 report testifies, already so happily attends the 

 operations of the different scientific departments 

 of the Indian Government. 



NO. 2548, VOL. lOl] 



PROF. PAOLO PIZZETTI. 



ITALIAN geodesy sustained a serious loss 

 by the death, on April 14, of Paolo Pizzetti, 

 professor of geodesy in the University of Pisa. 

 An account of Pizzetti 's work is contributed to 

 the Atti del Lincei, xxvii. (i) 9, by Prof. Vincenzo 

 Reina, and the following particulars are mainly 

 derived from it. 



Prof. Pizzetti was born at Parma in i860, and 

 at the age of twenty qualified in the Engineering 

 School at Rome. He afterwards remained there 

 as assistant to the Department of Geodesy at the 

 time when Profs. Pisati and Pucci had com- 

 menced their researches on the absolute value of 

 gravity. Prof. Pizzetti soon began to publish 

 researches dealing with the determination of 

 azimuth, conformal representation in geodesy, and 

 similar subjects. In December, 1886, he was ap- 

 pointed professor extraordinarius of geodesy at 

 Genoa, and while there devoted his main attention 

 to the theory of errors, with special reference to 

 combinations of observations; It was then that he 

 produced his important papers on the results of 

 a system of direct observations, published by the 

 Royal Society of Li^ge, and on the mathematical 

 foundations for the criterion of experimental 

 results, the last-named paper appearing in the 

 jubilee volume published in 1892 at the fourth 

 centenary of the discovery of America by 

 Columbus. We are indebted to Prof. Pizzetti 

 for clearing up many poihts of doubt regarding 

 the relative value of such concepts as measure of 

 precision, mean error, probable error, and error 

 of maximum probability. At the same time, 

 he interested himself in the study of atmospheric 

 refraction, on which he published papers dealing 

 with the trajectories of light rays and the difficult 

 problem of refraction in azimuth. 



In 1900 Prof. Pizzetti removed to Pisa, and in 

 the following year he took charge of the classes in 

 celestial mechanics. He here initiated an im- 

 portant series of researches dealing with the figure 

 I of the earth and planets, and with Stokes's formula 

 i for the potential of a gravitating planet, of which 

 I he gave a rigorous proof. Previously some doubts 

 ! existed as to the limits within which this expan- 

 sion was valid, and these were set at rest by 

 : Prof. Pizzetti's investigation. It is scarcely sur- 

 prising that he did not escape from the attrac- 

 tions of the ever-popular and seductive "problem 

 of n bodies." 

 I The bibliography at the end of Prof. Reina 's 

 nc'ace enumerates ninety-two papers by Prof. 

 j Pizzetti, mainly devoted to geodesy, astronomy, 

 and celestial mechanics, but including a few papers 

 I on pure mathematics and some reviews and articles 



of a more popular character. 

 I To the present writer the name of Pizzetti will 

 I ever be associated with reminiscences of a day at 

 1 Pisa at the conclusion of the Mathematical Con- 

 gress of Rome in 1908, where it was his privilege 

 to meet Prof. Pizzetti and his colleagues in 

 friendly intercourse in the " Sala dei Professori,'* 

 a room reserved for these informal gatherings at 



