444 



NATURE 



[June 2, 192 1 



Calendar of Scientific Pioneers, 



June 2, 1886. James Apjohn died.— A lecturer and 

 professor of chemistry at Dublin for more than fifty 

 years and a vice-president of the Royal Irish Academy, 

 Apjohn wrote on chemistry, mineralogy, and meteoro- 

 logy, and his name is connected \\'ith a formula for 

 ascertaining the dew-point. 



June 2, 1901. John Viriamu Jones died.— After a 

 distinguished career at Oxford, Jones in 1881, at the 

 age of twenty-five, became principal of Firth College, 

 Sheflfield, and two years later was made the first 

 Principal of University College, South Wales. His 

 principal scientific work referred to accurate deter- 

 minations of electrical and physical standards. 



June 2, 1903. Andrew Ainslie Common died.— An 

 engineer by profession, Common devoted himself to 

 the construction of large reflecting telescopes with 

 silver-on-glass mirrors. Harvard and Lick Observa- 

 tories possess instruments from his Ealing workshops. 

 He received the gold medal of the Royal Astrono- 

 mical Society for his photographs of the great nebula 

 in Orion, and in 1895-96 was president of the society. 



June 3, 1657. William Harvey died.— Born at 

 Folkestone on April i, 1578, Harvey was educated 

 at Canterbury, Cambridge,, and Padua, and, after 

 graduating in medicine, settled in London. Appointed 

 physician to St. Bartholomew's Hospital in 1609, six 

 years later he became Lumleian lecturer at the Col- 

 lege of Physicians, where he first publicly taught the 

 doctrine of the circulation of the blood. His celebrated 

 treatise, " Exercitatio Anatomica de Motu Cordis et 

 Sanguinis," was published at Frankfort in 1628. He 

 was physician to James L and Charles L His tomb 

 is at Hempstead, near Saffron Walden. 



June 3, 1822. Ren6 Just Haiiy died. — After many 

 early privations, Haiiy became a teacher in the Col- 

 lege of Navarre in Paris. An accident to a crystal 

 of calcareous spar led him to the discovery of the law 

 of crystallisation. His first memoir on the structure 

 of crystals appeared in 1784. He afterwards held im- 

 portant official positions, among which was the chair 

 of mineralogy at the Jardin des Plantes. 



June 5, 1716. Roger Cotes died.— In 1706, at the 

 age of twenty-four. Cotes became the first Plumian 

 professor of astronomy and patural philosophy at 

 Cambridge. He assisted Newton in the revision^ of 

 the " Principia," with Whiston gave one of the earliest 

 courses of experimental philosophy, and in Trinity 

 College erected an observatory. A man of excep- 

 tional genius, Newton, referring to his work on optics, 

 remarked: "If Mr. Cotes had lived we should have 

 known something." 



June 7, 1826. Joseph von Fraunhofer died. — A 

 glass-cutter's apprentice, Fraunhofer in 1804 became 

 associated with Reichenbach, the instrument-maker. 

 A skilful maker of telescopes, he invented the sta^e 

 micrometer, the diffraction grating, and a form of 

 heliometer. He discovered the dark lines in the spec- 

 trum previously seen by WoUaston, and laid the 

 foundations of solar and stellar chemistry. 



June 8, 1695. Christiaan Huygens van Zuylichem 

 died. — The greatest of Dutch physicists, Huygens is a 

 connecting link between Galileo and Newton. Born 

 at The Hague in 1629, he spent many years of his life 

 in Paris. He improved the telescope, discovered the 

 first of Saturn's satellites, explained the nature of 

 Saturn's ring, adapted the pendulum to clocks, and 

 advocated the undulatorv theory of light. His prin- 

 cipal works were his "Traits de la lumi^re " and his 

 " Horologium Oscillatorum." He is buried In St. 

 Peter's, Leyden- E. C. S. 



NO. 2692, VOL. 107] 



Societies and Academies. 



London. 

 Royal Society, May 26.— Prof. C. S. Sherrington, 

 president, in the chair. — Sir Alfred Ewing : The 

 atomic process in ferro-magnetic induction. The 

 author's modification of Weber's theory of magnetisa- 

 tion is reconsidered in the light of (i) modern views 

 regarding the structure of the atom and (2) the X-ray 

 analysis of crystal structure. The rotatable Weber 

 magnet seems to be an attribute of the atom, prob- 

 ably an electron system within it. Metallic iron is 

 now known to be an aggregate of crystals, in each of 

 which the space-lattice is the centred cube, with Its 

 atoms most closely grouped along the trigonal axes. 

 It is along these axes that the Weber elements will 

 point. Consequently an iron crystal is not mag- 

 netically isotropic. The small quasi-elastic or re- 

 versible part preceding the much larger changes which 

 involve hysteresis corresponds to a reversible deflec- 

 tion of the Weber magnets through a small angle, 

 generally of an order of 1°. The theory of the equili- 

 brium of a row of magnets is considered. Experi- 

 ments In which rows of Robison magnets with ball 

 ends have their equilibrium upset by an extraneous 

 field confirm the theory. The field which would break 

 up rows of magnets set in the space -lattice close 

 enough together to bring the reversible deflection 

 within the above limit is calculated ; It Is larger than 

 the field that suffices to produce strong magnetisation 

 In Iron, suggesting that the ordinary laws of force 

 between magnetic elements cease to apply at inter- 

 atomic distances. — C. D. EUis : The magnetic spec- 

 trum of the ^-rays excited by the 7-rays. The mag- 

 netic spectra of the /?-rays ejected from various 

 elements by the 7-rays of radium B have been 

 examined by the focussing method. The positions of 

 three strong lines occurring in the magnetic spectrum 

 of radium B depend on the metal target used. Assum- 

 ing that each of these three lines Is due to a definite 

 7-radiatIon, It is shown that the energy of the j8-ray« 

 forming a line is equal to an energy characteristic of 

 the 7-radIation minus the work necessary to remove 

 an electron from the K ring of the atom. By applica- 

 tion of the quantum theory the frequency of the 

 7-rays can be determined from these characteristic 

 energies. The natural jS-ray spectrum of radium B 

 can be explained in this way, the stronger lines result- 

 ing from the conversion of the 7-rays In the K ring, 

 and the weaker lines from a similar conversion of the 

 same 7-rays In the L ring. — S. Datta : The spectra of 

 the alkaline earth fluorides and their relation to each 

 other. A survey of the spectra of these compounds 

 has been made and several new bands observed. 

 These helped in the identification of homologous series 

 of bands in the different spectra, and have suggested 

 an empirical relation amongst them, based on the 

 constants of the series equations and the molecular 

 weight or the molecular number of the respective 

 compounds. Starting with the series equation of the 

 band-heads, an explanation has been given of the 

 appearance of a "tail " In some of the bands. It has 

 been shown that the frequency of the "tail " is a 

 maximum or a minimum, and that the difference In 

 wave-numbers of the heads and tails of the similar 

 series Is constant for the same compound, but varies 

 from one another In a definite way. — Dr. W. L. BalU : 

 A simple apparatus for approximate harmonic analysis 

 and for periodlcltv measurements. The error Involved 

 In the use of this apparatus need not exceed 3 per 

 cent. Its outstanding advantage Is the speed with 

 which determinations may be made. Thus In deter- 

 minations of oeriodicltv some fifty trial periods can 

 be examined In less time than is required for the 



