474 



NATURE 



[September 6, 1906 



without a definite solution. Messrs. M. Padoa .'aid B. 

 Savart in the Gazzetta (vol. xxxvi., p. 310) have attacked 

 the problem in a new way by investigating the change in 

 the electrical conductivity of a solution of iodine in 

 potassium iodide caused by the addition of starch in known 

 proportions. The conclusion is drawn from their experi- 

 ments that the blue substance is an additive compound of 

 iodine, starch, and potassium iodide (or hydrogen iodide) 

 containing the two former constituents in the ratio 

 ' • C„H,„05 = i : 4. While this result supports the opinion 

 of Mylius, enunciated some twenty years ago, it is directly 

 opposed to the more recent view of Kiister that the blue 

 substance is not a definite substance, but is formed as a 

 result of adsorption by the colloid starch. Kiister's conten- 

 tion recently received striking support by the work of 

 Biltz in 1904, who showed that basic lanthanum acetate, 

 which resembles starch in its colloidal nature, also pro- 

 duces with iodine an intensely blue substance similar in 

 all respects to that formed from starch ; in this case there 

 seems to be no evidence to consider the substance as a 

 definite chemical compound. 



The current issues of the Lancet and the British Medical 

 Journal are educational numbers, and are entirely devoted 

 to communications bearing upon preparation for the medical 

 profession. 



The Royal Geographical Society has issued through Mr. 

 E. Stanford a general index to the first twenty volumes of 

 the Geographical Journal, 1893-1902. The work, which is 

 divided into three parts, devoted respectively to papers, 

 maps, and general subjects, should prove a boon to 

 geographers. 



The third edition of Prof. R. von Weltstein's " Leitfaden 

 der Botanik fur die oberen Klassen der Mittelschulen " 

 has just been published by Mr. F. Tempsky, Vienna. The 

 book contains 236 pages, more than half of which (134 

 pages) are devoted to systematic botany, while the remain- 

 ing sections deal with plant anatomy, organography, 

 physiology and ecology, geography, and economic botany. 

 There are three coloured plates and more than a thousand 

 figures upon 205 blacks. Within its limits, the work makes 

 an admirable survey of the realm of botany, being attractive 

 in illustration, concise in description, and sound in sub- 

 stance. 



OUR ASTRONOMICAL COLUMN. 



Return of Holmes's Comet (1906/).— The remarkable 

 comet discovered by Mr. Holmes on November 2, 1892, has 

 been re-discovered on this, its second, return by Dr. 'Max 

 Wolf at the Konigstuhl Observatory, Heidelberg. From 

 the Kiel telegram announcing this fact we learn that on 

 August 28, the date of the observation, the comet's position 

 at i3h. 52-im. (Konigstuhl M.T.) was 



R.A.=4h. 7m. 24s., dec. = -1-42° 28'. 

 This position is between one-third and one-half the distance 

 between 52 and 53 Persei, and crosses our meridian at about 

 5.30 a.m. 



Comparing the position with that given by the ephemeris 

 published by Dr. H. J. Zwiers in No. 4085 of the Astrono- 

 mische Nachrichten, we find that small corrections of about 

 -t-o-sm. in R.A. and -1-3 '-5 in declination need to be 

 applied to the latter. A portion of this ephemeris is given 

 hereunder : — 



Ephc 



oh. (M.T. Grcc 



i(app.) SCapp.) 



Ch). 



Sept. 6 



Comet 19062 (Kopff). — Circular No. 90 from the Kiel 

 Centralstelle gives three ephemerides for the comet recently 

 discovered by Herr Kopff at Heidelberg. The following 

 was computed by Herr M. Ebell : — 



1906 



h. m. s. 



Sept. 4 ... 22 39 58 



8 ... 22 37 19 



12 ... 22 34 57 



16 ... 22 32 55 



Ephemeris 12ft. (Berlin M.T.). 



log . 



Brigbtn 



+ 9 36'o 

 + 9 14-9 

 + 8 52-0 

 + 8 28-1 



0-0490 ... 075 



o 0639 ... o 67 



0-0797 ... 0-60 



o-og6i ... 0-54 



Several observations of this comet are recorded in No. 

 41 17 of the Astronomische Nachrichten. Prof. Kobold, 

 observing at Kiel on August 23, saw it as an undecided, 

 round spot of 2' diameter with a central condensation of 

 magnitude ii-o. The magnitude of the whole was 10-5. 

 From an observation, also made on August 23, Prof. 

 Hartwig described it as having a diameter of i'-5, a nucleus 

 of magnitude 13-0, and a round shape, the total magnitude 

 being 12.0. 



A Newly-discovered Planetary Nebula. — On examining 

 one of the plates taken with the lo-inch Brashear lens of the 

 Bruce photographic telescope. Prof. Barnard discovered the 

 image of a fine planetary nebula which does not appear 

 to be in the catalogues. The approximate position of the 

 nebula, for 1855, is o=iih. 7m., 5 = -his° 42'. In the 

 same region there appear to be quite a number of spiral 

 nebulae and nebulous stars (Astronomische Nachrichten, 

 No. 41 12). 



Plea for an International Southern Telescope. — In 

 No. 182, vol. xlv., of the Proceedings of the American 

 Philosophical Society Prof. E. C. Pickering advances a 

 businesslike plea for the institution of a large international 

 rellector in the southern hemisphere. He points out that, 

 under the existing conditions, it is hard to see how any 

 great step may be made in the advance of astronomy, but 

 thinks that if a reflector of about 7 feet aperture and 

 44 feet focal length were erected in the best possible atmo- 

 sphere to be found in the southern hemisphere, advances 

 of immense importance might accrue. The cost he 

 estimates at something less than 500,000 dollars (rather 

 more than ioo,oooi.), and he suggests that such a scheme 

 would be an eminently suitable one by which to com- 

 memorate the Franklin bi-centenary. 



THE PROGRESS OF AGRICULTURAL 



SCIENCE. 



'T'HREE years ago the Royal Agricultural Society con- 



ceived the happy idea of holding, in connection with 

 its annual shows, an agricultural education exhibition, at 

 which the work of the various agricultural colleges might 

 be brought prominently before the public, and especially 

 the latest results of agricultural scientific research. The 

 fourth annual exhibition of this kind was recently held at 

 Derby, and the object of this note is to indicate several 

 of the more important directions which agricultural research 

 and rural education are now taking, and the results as 

 illustrated at the exhibition. 



Mendel's Laws of Inheritance. 

 Important hybridising experiments on the lines of 

 Mendel's laws of inheritance are being carried out at the 

 Cambridge University Agricultural Department by Mr. 

 R. H. Bififen. Mendel's laws prove the recurrence in 

 breeding of dominant and recessive characters in certain 

 definite proportions, and their application renders possible 

 the production of new fixed types in two or three gener- 

 ations with mathematical precision instead of as formerly 

 after years of more or less haphazard breeding by selec- 

 tion. Thus in crossing smooth red with rough white 

 wheat, the first cross was apparently of fixed type ; but in 

 the second generation only one out of sixteen bred true ; 

 in the third generation three bred true ; in the fourth 

 generation four bred true, and the type was fixed. The 

 same principles are applicable to the inheritance of disease. 

 Rows of wheats were shown proving the possibility of 



