100 



DISCOVERY 



Mention was made in Mr. Darwin's article, in the 

 second number, of the work of Mr. Aston at Cambridge 

 on the purity of chemical elements. Mr. Aston first 

 showed that the gaseous element neon is really com- 

 posed of two gases the atomic weights of which are 

 20 and 22. He also showed that " pure " chlorine 

 really consists of two gases of atomic weights 35 and 

 37. Nitrogen (atomic weight 14) and Carbon (atomic 

 weight 12) appear to be "perfectly pure" — that is to 

 say, not a mi.xture of two or more elements of almost 

 identical properties, as are neon and chlorine. He has 

 extended his results recently to other elements. Argon 

 is found to consist of two gases of atomic weights 36 

 and 40 ; krypton of six gases, xenon of five gases, 

 and mercury of a mixture of elements of atomic 

 weights 204, 202 certainly, and of others about 197 to 

 200 in atomic weight. Helium (atomic weight 4) is 

 found to be " perfectly pure." These results will be 

 of extraordinary interest to all students of natural 

 science. That a chemical element in its purest form 

 should, all the time, be really a mixture of elements, 

 which no ordinary chemical or physical process can 

 separate, is a matter of great importance. In all cases 

 which Mr. Aston has so far investigated, with the 

 single exception of hydrogen, the atomic weights of 

 these constituent elements, the " isotopes," are whole 

 numbers. 



***** 



The great interest of Einstein's General Theory of 

 Relativity may justify a brief note about his career. 

 The following details were kindly supplied by Dr. E. 

 Freundlich. Albert Einstein was born in March 1879, 

 in Ulm in Wiirtemberg. His school years were spent 

 in Munich. He early showed promise of an unusually 

 brilliant future. He studied physics and mathematics 

 at Zurich University from 1896 to 1900. On attain- 

 ing his majority he changed his nationality by be- 

 coming a citizen of Zurich. During the next seven 

 years he was engineer to the Patent Office, Bern. His 

 first great achievement, the special Theory of Rela- 

 tivity, was enunciated in a paper read to the Berlin 

 Academy of Sciences. It was soon followed by others 

 dealing successively with the inertia of all forms of 

 energy, the Brownian movement, and the Quantum 

 Law of the emission and absorption of light. He 

 became Professor Extraordinarius at Ziirich in 1910, 

 and later full professor at Prague, but returned to a per- 

 manent post in Zurich in the following year. The 

 fundamental notions of his epoch-making theory, which 

 has undermined the traditional conception of space, 

 were evolved in 1907 ; but his attempts to solve the 

 elusive problem of gravitation only began to show 

 signs of success in 191 2, when he recognised how 

 much more simply gravitational phenomena could be 

 interpreted by adopting non-Euclidean space. In 



1914 he migrated to Berlin, where he has since re- 

 mained. His general theory of relativity was made 

 known to the BerUn Academy of Sciences in 1915, 

 when he established the equations of the gravitational 

 field, and succeeded in explaining mathematically the 

 behaviour of the motion of Mercury's perihehon, which 

 had long been a source of mystery to astronomers. 



In addition to his scientific attainments, he is deeply 

 devoted to the Zionist cause, and is a keen inter- 

 nationalist. He is also an accomplished vioUnist. 

 During the war several of our men interned in Berlin 

 found in him a good friend. 



The Date of the Nativity 



By W. M. Calder, M.A. 



Projessor o/ Greek in the Vnioersity of Manchester. 



It is well known that Christ was bom some years 

 before the date of the " Birth of Christ," which forms 

 the starting-point of the Christian Era.* Luke in all 

 probability intended to imply, and Matthew definitely 

 states, that Christ was bom before the death of King 

 Herod, who ordered the " Massacre of the Innocents " ; 

 and we know for certain that King Herod died early in 

 4 B.C. Recent discovery — or discovery which would 

 have been called " recent " in 1914 — has thro\Tn fresh 

 hght on the events which, in Luke's narrative, form 

 the setting of the birth of Christ. We cannot yet 

 assign the Nativity to a definite year, but many old 

 difficulties have been cleared away, and the choice 

 of a possible date has been restricted within narrow 

 limits. At the invitation of the Editor, I will attempt 

 to indicate briefly the character of the problem, and 

 the bearing of the new evidence on its solution. 



The words of Luke are as follows (ch. ii. 1-4) : 

 " Now it came to pass in those days, there went out a 

 decree from C;esar Augustus that all the [Roman] 

 world should be enrolled. This was the first enrol- 

 ment, made when Quirinius was governing Syria. And 

 all went to enrol themselves, every one to his own city. 

 And Joseph also went up from Galilee, out of the city 

 of Nazareth, into Judaa, to the city of David, which is 

 called Bethlehem, because he was of the house and 

 family of David — to enrol himself witli Marj' his wife, 



• How this traditional date was arrived at in the third and 

 fourth ccnturicE ad. does not concern us here. Information 

 on the matter may be sought under the articles Eusebius 

 and Jerome in the Encyclopadia Britannica (ed. xi). 



