October 15, 1891] 



NATURE 



565 



Attention is for any reason especially directed to South 

 Africa. It includes several excellent maps, and two en- 

 gravings of Cape Town, showing Cape Town as it was 

 in 1668, and as it is in 1891. 



LETTERS TO THE EDITOR. 

 [The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Ndther can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of 'iHATVKV.. 

 No notice is taken of anonymous communications.'^ 



A Pink Marine Micro-organism. 



While dredging lately in Loch Fyne, I noticed through the 

 clear water, in a little shallow bay on the north side of the 

 entrance to East Loch Tarbert, a number of pink patches on 

 the sand. These could just be reached by wading from a boat 

 at the lowest tides, and were then found to be roughly circular 

 spots, about a foot in diameter, where the clean white sand was 

 discoloured, most of the surface grains being almost exactly the 

 tint of ordinary pink blotting-paper. 



Under a low power of the microscope, it is seen that the pink 

 particles are ordinary clear quartz sand-grains, incrusted with 

 little bright pink jelly masses, generally of elongated or sausage- 

 like forms, and averaging 01 mm. in length. Further mag- 

 nification shows that each jelly mass is crowded with minute 

 very short rods, or ellipsoids, of about 0*0015 ™ni' in length, 

 and about half as much in breadth. 



This appears to be a micro-organism in the zooglcea condition, 

 and I do not know that any such pink marine form, living on 

 clean sand, in pure sea water, has been noticed. It may possibly 

 be one of the forms of Beggiatoa rosea-persicina, but it does 

 not agree satisfactorily with any of the descriptions I have 

 access to here. I have still some of the material alive in sea 

 water, and shall be glad to hand it over to any biologist who is 

 now working specially at such forms, and would like to inves- 

 tigate this one. W. A. Herdman. 



University College, Liverpool, October 6. 



Advertisements for Instructors. 



The friends of technical education can no longer complain 

 that the subject is not receiving attention* The numerous ad- 

 vertisements for instructors of all sorts, from County Councils 

 and other bodies, colleges and schools are full evidence that 

 much is being attempted. 



Whether all the plans and proposals and experiments will 

 lead to the hoped-for results only time will show. Some of us 

 have our doubts as regards many of them. 



Meantime, one of the advertisements deserves a passing 

 notice. A well-known technical school is in search of "a 

 demonstrator in the Metallurgical Department to take the lec- 

 tures in geology and mineralogy, and to give instruction in 

 dry assaying and in iron and steel analysis" (see Nature 

 of this week). 



This is certainly a large and considerably mixed "order," 

 calculated to make thoughtful people wonder what sort of in- 

 struction is expected to be given by this gifted person (who is 

 to have the princely sum ef ;,^ioo per annum) ; and whether, if 

 the "metallurgical demonstrator" is to throw in geology 

 and mineralogy as a sort of extra to his own special work, the 

 other demonstrators and professors are expected to be equally 

 widely qualified ; let us say a chemical demonstrator to give 

 lectures on mechanical engineering and ship-building ? 



Newcastle-on-Tyne, October 10. M. 



"Rain-making." 



I THINK the following will be of interest to your readers in 

 connection with the "rain-making" experiments in Texas. On 

 October i, at 5 p.m., five tons of gunpowder was exploded 

 in a single blast at the Penrhyn slate quarries in order to clear 

 away a very large mass of useless rock. A strong wind had 

 been blowing all day, and the clouds, though heavy, were high ; 

 there had been no rain, and not much sunshine, and the tem- 

 perature was somewhat low. 



Immediately after the explosion the wind fell to a dead calm, 



NO. II 46. VOL. 44.1 



which lasted about 5 or 6 minutes, and 20 minutes later a 

 fine rain began to fall, which soon became heavy and continued 

 for an hour and a half By 7 p.m. all disturbances produced by 

 the explosion had apparently passed away, and the weather was 

 again similar to what it had been during the day. The rainfall 

 was entirely local, there being none, as far as I could learn, 

 outside a radius of 6 or 7 miles from the quarry. 



W. R. PiDGEON. 



Alum Solution. 

 With reference to the question raised by Mr. H. N. Draper 

 in Nature, vol. xliv. p. 446, as to the practical superiority of 

 an alum solution over simple water in absorbing such radiations 

 as are chiefly instrumental in producing heat, I may recall some 

 experiments made by myself five years ago (Brit. Assoc. Report, 

 1886, p. 309). Thesonrceofradiationemployedwas a paraffin lamp 

 with a glass chimney, the various solutions were contained in a 

 glass cell with parallel sides, and the "radiometer" was a deli- 

 cate thermopile, the face of which was blackened with camphor 

 smoke. The following results, among others, were obtained : — 

 Solutions, &c. Diathermancy. 



Empty cell 1000 



Water distilled 197 



Water from tap 200 



Alum, saturated solution 204 



It is clear therefore that, at least under condiiions like those 

 of my experiment, plain water will answer the purpose of an 

 absorbent rather better than an alum solution. Possibly the 

 "alum cell" tradition rests upon no better foundation than many 

 others, which are generally accepted simply because it does not 

 occur to people to question them. 



Shelford Bidwell. 

 October 10. 



B.Sc. Exam. Lond. Univ. 1892. 



There are, I believe, in London at the present time a number 

 of men desirous of offering geology as one of three subjects 

 required at the Degree Examination in Science, but who are 

 deterred from so doing by the fact that it is impossible to 

 obtain adequate evening class tuition in this subject. 



Enquiries at the various teaching institutions have failed to 

 discover a single opportunity for working up to the required 

 standard in both theoretical and practical branches. 



I have therefore laid the matter before Prof. Wiltshire, of 

 King's College, Strand, with the result that he has very kindly 

 consented, in the event of enough men requiring it, to supple- 

 ment his lectures on geology and mineralogy by a course of in- 

 struction in petrology, embracing the study of hand specimens 

 and microscopical examination of rock sections. 



By giving publicity to the matter, it is hoped that a sufficient 

 number of B.Sc. candidates will be forthcoming to ensure the 

 establishment of this class. 



The time-table for the complete course will be as follows : — 



( Petrology ... 6-7 p.m. 

 Monday < Mineralogy ... 7-8 ,, 

 ( Geology ... 8-9 ,, 



The lectures and practical work, together with the summer 

 field excursions, under the direction of Prof Wiltshire, will 

 prove a great boon to such as are prevented from attending day 

 courses, and will undoubtedly secure admirable preparation for 

 the examination specified. 



I shall be glad to hear from anyone interested in the matter, 

 so that arrangements may at once be made for the first sitting 

 to take place on Monday, October 19. 



Edward J. Burrell. 



People's Palace, Mile End Road, E. 



Some Notes. 



Those who have visited Venice in spring know how rampant 

 mosquitoes become after the flight of the swallows, which have 

 kept them in check, for the north — usually in May. 



A word for the sparrows — which have been very active in the 

 gardens hereabouts this season, preying on the green flies and 

 larva- infesting the creepers and ferns in particular ; but very 

 few starlings have been observed, to the great increase of earth- 



