July io, 19 13] 



NATURE 



487 



OUR ASTRONOMICAL COLUMN. 

 The Hottest Stars. — Under this heading, Dr. Ant. 

 Pannekoek communicates a short note to the Astro- 

 nomische Nachrichten, No. 4657. It relates to the list 

 of spectral-photometric measures made by Herr H. 

 Rosenberg (see this column, May 29) of the- 

 temperatures of the hotter stars. Dr. Pannekoek 

 states that from this list a regular increase of the 

 figures takes places with the class-number of the 

 spectra according to Miss Maury's classification. 

 Whether this increase commences at the beginning 

 or in which class the helium or the whitest or hottest 

 stars are to be found cannot be clearly stated in 

 consequence of the few stars discussed. Dr. Panne- 

 koek utilises the large quantity of material available 

 in the catalogue of colour-estimations by Ostholf, and 

 while they give no results of absolute temperature, 

 they are of value from a relative point of view. The 

 comparison of these values with Miss Maury's types 

 brings out the result that lowest colour number corre- 

 sponds with her class IV. or IV.-V., or the typical 

 helium stars. On either side of these classes the 

 colour numbers increase, and the temperature de- 

 creases not only on the side of the Sirian stars of 

 the first type, but also toward-; the YVolf-Rayet stars. 

 The following is the complete table which he gives 

 in the paper,' but here Miss Maury's classes are pre- 

 ceded by the equivalents in Sir Norman Lockyer's 

 classification for comparison : — 



Class 

 (Lockyer) 

 Argonian 

 Alnitamian ... 

 Crucian 

 Crucian, Achernian 



Taurian, Algolian ... 

 Rigelian, Algolian ... 

 Algolian, Markabian 

 Cygnian, Markabian 



Sirian 

 Sirian 

 Procyonian ... 



Pol avian, Procyonian 

 Polarian, Procyonian 



Arcturian ... 



Arcturian ... 



Arcturian 

 Arcturian ... 



Aldebaiian ... 



Antarian 



Antarian 



Antaiinn 



A Photo-visual Comparator for the Identifica- 

 tion of Minor Planets. — As the only means whereby 

 a minor planet is distinguishable from a star of the 

 same magnitude is its proper motion, its identifica- 

 tion is often a matter of considerable labour propor- 

 tional to the planet's magnitude and the uncertainty 

 of the ephemeris. To this end M. J. Lagrula employs 

 an ingenious arrangement which he describes in a note 

 presented to the Paris Academy of Sciences (Comptes 

 rendus. No. 15). It consists of a binocular combina- 

 tion of telescope and microscope, forming what is 

 essentially a stereo-comparator, in which a coloured 

 image of a photographic positive of the region to be 

 examined is superposed on the image seen in the 

 telescope. All objects visible in the field of the tele- 

 scope, except small planets which have no counter- 

 part on the photograph, are distinguished by the 

 presence of a coloured disc. For use with the Gautier 



NO. 2 28o, VOL. 91] 



equatorial of the Nice Observatory copies of the 

 photographic charts of MM. Palisa and Wolf have 

 been found eminently suitable. As an example of the 

 rapidity and efficiency of operating with the device 

 the author instances detecting within five minutes 

 an error in the published ephemerides of (3) Asterope. 



Meteor Dust as a Measure of Geologic Time. — 

 In Science, No. 957, Prof. Alfred C. Lane directs 

 attention to the possibility of using the proportion 

 of contained meteor dust as a measure of the rate . 

 of formation of strata, and heme as a criterion of 

 geologic time. He calculates that the earth gains 

 20,000 grams of cosmically derived nickel per square 

 kilometre per annum. From this figure and the 

 nickel content of the abysmal red clay he estimates 

 that a laver one metre 'thick of the latter requires 

 8700 years to accumulate. The professor urges mem- 

 bers of proposed polar expeditions to complete 

 Nordenskjold's observations by determining the rate 

 of deposition of cosmic dust, and optimistically anti- 

 cipates that within this century there will be drilled 

 a hole in the bottom of the sea which will give us 

 the other datum to be determined. 



THE ROYAL AGRICULTURAL SHOW. 



THE extremely successful Royal Show held at 

 Bristol, Julv 2-5, illustrated in a striking way 

 the general progress being made in agriculture, horti- 

 culture, and forestry, but presented very little calling 

 for comment from the scientific point of view. Among 

 livestock, a remarkable novelty was the pen of primi- 

 tive breeds of sheep — and crosses from the same — 

 exhibited by Prof. Cossar Ewart and Mr. H. J. 

 Elwes. This throws some light on the origin of 

 domesticated sheep, and also suggests the possibility 

 of establishing one or more new breeds capable of 

 thriving on poor upland pastures in this country, and 

 of yielding more valuable wool than that of the 

 ordinary hill-breeds. 



In the Agricultural Education Exhibition, Rotham- 

 sted showed an interesting series of tomato-plants in 

 pots to demonstrate the advantage of partial sterilisa- 

 tion of soil in various ways. Wye College— as usual 

 —exhibited a striking series of pests, fungoid (in- 

 cluding a new disease of apple-buds) and insect 

 (some'in the living state). The University of Bristol 

 was represented by the associated Royal Agricultural 

 College (received in deputation by H.M. the Kins: 

 on July 4) and Long Ashton Fruit and Cider Insti- 

 tute. "The chief feature of the former was a collec- 

 tion of wool-staples, including a series from the sheep 

 in the above-mentioned exhibit of Ewart and Elwes. 

 Long Ashton, as the chief British horticultural re- 

 search centre, is evidently working with increased 

 energy since its reconstitution and extension, and one 

 of it's most interesting exhibits consisted of specimens 

 of a new disease of pear-blossoms, due to bacteria as 

 yet unnamed, and causing the young fruits to _ fall 

 early. The Nature-study Section, including exhibits 

 from several western and south-western counties, was 

 a decided improvement on past years, proving 

 that school work is now more systematic than 

 formerly. Gloucestershire is to be -congratulated 

 on classifying its material by subjects and not by 

 schools. 



The exhibit of British tobaccos attracted much 

 notice, but most of those who sampled the specimens 

 were not impressed by their quality, though no doubt 

 home-grown material may prove useful for fumigation 

 purposes. The Forestry Section was particularly 



