LAND KKC.ISTRAT ION IN .M( )ZA .M 1' lOl'K. 421 



projjerty, will guarantee sufiicient reniuneralion to those obtain- 

 ing- the respective (li])lomas for ^geometrical survey work. 



With the above, I have concluded all that is possiljle to con- 

 dense in a paper concerning the cadastre of immovable i^roperty 

 in Mozaml)i(|ue, the interest of which, as mere " news value," 

 consists in the fact that a system which deals with property on 

 the basis of legal and geometrical surve\- and registration and 

 the fiscal ])art of which will in the future tind in the same 

 records the required data, is exclusive to this I'ortuguese Oversea 

 Province. 



The Constitution of Nebulae.— At a recent 



meeting of the Royal Astronomical Society, Prof. I. W. 

 Nicholson, M.A., D.Sc, said that it is probal^le that the main 

 constituent of the i^lanetary nebuhe. and of others, such as the 

 great nebula in ( )rion, is an element, to which the name Xebulium 

 is assigned, with a i)recisely indicated atomic structure. It mav 

 not be strictly an element of the type found in the Periodic 

 Table, but must be regarded as an origin from which other 

 elements may spring. From his investigations Dr. Nicholsoii 

 infers that nebuL'e consist of ( i ) simple-ring systems, with 

 simple nuclei ; ( 2 ) the hrst products of an evolution of some 

 form from these systems; and (3) hydrogen and helitmi, the 

 simplest terrestrial elements. The chemical substance of the 

 nebulae, therefore, consists of the very beginnings of matter, and 

 spectrum of a nel)ula may be described as the spec- 

 trum of chaos. Whatever may occur with terrestrial atoms, 

 the electrons in a nebula are not held very firmly in the atoms, 

 and a continued interchange of electrons must be taking place, 

 with a necessary boml^ardment of atoms l)y free electrons, to 

 which the luminosity is probably due. The physical state of a 

 nebula must l)e analogous to that of a very exhausted \acumn 

 tube of enormous extent. Two days prior to Dr. Nicholson's 

 communication to the Royal Astronomical Society MM. Bourget. 

 Fabry, and Buisson published in Comptcs Reudns some results 

 of their in\estigations into the subject of the atomic weight of 

 nebulium and the temperature oi the ( )rion nebula. Referring 

 to the spectrum of the nebula, they say that the ver\- marked 

 double line 3726 — 3729 in the ultra-violet ])art of the sjiectrum 

 is not attributable to any known gas. From a calculation of the 

 limiting order of interference — a function of the atomic weight 

 and the absolute temperature — it is found that the atomic weight 

 of the unknown gas — nebulivmi — is a])out 3. The maximum 

 temperature of the luminous gas is a])OUt 15,000°. A strong 

 green ray, also due to an unknown gas, is emitted by a gas of 

 atomic weight greater than that of hydrogen, but less than that 

 of the gas emitting the ultra-violet ray. This is of interest in 

 view of the fact that, in Rydberg's recent classification of the 

 elements, there are two unknown elements between hydrogen 

 and helium whose atomic weights are respectively 2 and 3. 



