September, 1912. 



KNOWLEDGE. 



343 



proved for three thousand five hundred feet, and in that 

 distance drops from an elevation of eleven thousand to about 

 nine thousand nine hundred feet. This may be tal<en as good 

 presumptive evidence of a corresponding continuity of the 

 deposit in depth. At a conservative estimate this deposit 

 would yield thirty thousand tons of potash (KoO) for each 

 hundred feet in depth. This is approximately one-sixth to 

 one-seventh of the total annual consumption of potash in the 

 United States. 



METE()R()L()G^■. 



By John A. Curtis, F.R.Met.Soc. 



GLOHL'LAR LIGHTNING.— An interesting accouni of 

 this somewhat rare phenomenon h.is been furnished by Mr. 

 S. Biggs, of Mazoe, South 

 Rhodesia, who reports that 

 in September, 1910, at about 

 9 p.m., he observed a ball of 

 fire, the colour of an electric 

 light, about one foot six inches 

 by ten inches in size, and 

 similar in shape to a Rugby 

 football. The ball was luminous 

 and transparent, but it cast 

 no light beyond its own body. 

 When first seen it was 

 stationary over a road on 

 Mr. Biggs' farm, and it 

 remained in one position for 

 about five minutes, during 

 which time Mr. Biggs 

 approached within three yards. 

 The light then moved away in 

 a zig-zag fashion at a rate of 

 about six miles an hour, and 

 finally entered a belt of trees, 

 where it disappeared, leaving 

 no trace whatever of its flight. 

 No noise was heard, no trace 

 of damage could be found, 

 and no smell could be 

 detected. 



MICROSCOl'V. 



By F.R.M.S. 

 A BLUE SCREEN. — Take an unexposed process plate; 

 fix it out in the dark with "hypo" ; wash well. Now fix the 

 gelatine film with formalin (ten per cent, or any convenient 

 strength) as if it were a histological preparation ; this may 

 take several hours. Wash well and stain with aqueous 

 solution of saureviolett (Grubler). Wash and dry. An 

 excellent screen is thus produced, which will transmit only 

 the blue and about half of the green. The intensity is modified 

 by the completeness of the formalin fixation, but if this is 

 omitted the results will be very unsatisfactory. The best 

 plan is, therefore, to give plenty of time. I made my staining 

 solution by adding water to a saturated solution of the dye- 

 stuff (which appears to be disulphonated dimethyldiethylpara- 

 rosanilin) in seventy per cent, alcohol. The time of staining 

 varies according to circumstances : it is, perhaps, best to leave 

 the plate until no further staining action is observed. 



E. W. BOWELL. 



MILES OF GREEN WATER.— Anyone who noticed the 

 Regent's Canal in July must have been struck by the colour 

 of the water. From the bridges it appeared of a dark green, 

 quite unlike its usual aspect. From the tow-path the water 

 was seen to be full of flocculent matter, diffused through it ; but 

 in corners and where the sluggish current was checked by barges 

 or other obstructions the minute bodies collected and formed 

 masses, floating on the surface like thick green grease or 

 paint. The appearance \vas caused by the presence in 

 astonishing quantities of a minute plant, one of the blue- 

 green algae, an Oscillatoria ; namely, O. agardhii Gom. 



This consists of extremely thin threads of various lengths, 

 composed of cells, filled with pale green protoplasm. It is 

 this which gives the colour, so noticeable owing to the 

 immense number of the organisms. The cells have also 

 in them several variously shaped, highly refractive bodies 

 (see Figure 371), generally considered to be " gas vacuoles." 

 Like other oscillatorias this one has a motion of its own, 

 in addition to that afforded by the flow of water. It 

 bends slightly backwards and forwards (oscillates — hence 

 the name), and also progresses slowly through the water. 

 It measures from four to five microns in diameter. In 

 1909 the same organism was present in the reservoir at the 

 Welsh Harp, Hcndon, in a similar manner. Vide Journal of 

 the Otickctt Microscopical Club. Series 2, Vol. XI, No. 67, 

 page 115, ct scq. I was told that the outbreak extended 

 for more than twenty miles 

 through the canal. There 

 were present also considerable 

 numbers of a minute spherical 

 alga, with a very similar 

 colour. It collects into irregu- 

 larly-shaped bodies of ditferent 

 sizes, but never very large, 

 each imbedded in a little mass 

 of gelatinous matter. The 

 composing units are about 

 3-5 M in diameter; it is called 

 Mycrocystis. A sample of 

 the water collected had the 

 remains of a number of 

 Entomostraca floating on the 

 surface, but I saw none alive. 

 It was possible to identify the 

 shells of Bosiitiiia, and per- 

 haps Cliydoriis, also that of 

 Cypris. but the only living 

 representative was the inevit- 

 able Cyclops, which seemed 

 to be enjoying its usual health 

 and activity. 



Rotifera were very numerous 

 and lively, Brachioiius bakeri 

 and, I think, B. iirccolaris 

 and a Philodina, besides some smaller species were 

 present. Brachioiius was feeding on the oscillatoria, 

 and it was interesting to watch it get the end of a long 

 (comparatively) filament into its mouth, the end passing 

 down to the mastax, which then worked vigorously at it ; 

 reminding one of a rabbit gradually drawing in and eating 

 a grass stem. .^11 of them showed the green of the alga in the 

 mastax, and it was quite evident that the plant was not 

 deleterious in its effect on them, as it is Credited with being on 

 fish. It is not easy to represent the refractive bodies in the 

 oscillatoria ; they change with the slightest alteration of focus, 

 but Figure 371 shows — highly magnified — some filaments, and 

 a few of the Microcystis drawn to the same scale. 



Jas. Burton. 



THE CUNEATE MARKINGS OF INSECT SCALES.— 

 Readers of " KNOWLEDGE " are familiar with this subject 

 through the articles and correspondence that have recently 

 appeared in these columns, on the structure of " Podura " 

 scales. The present writer has recently pursued some investi- 

 gations into the nature of the markings of one of the 

 Lepismidae (Therinobia doniestica) the results of which 

 have been communicated to the Royal Microscopical Society. 

 A summary of the conclusions arrived at may be of some 

 interest to those who have followed up the subject. In the 

 first place it may be stated that the scales from Thcrmobia 

 damestica are larger than " Podura " scales, and in many 

 respects similar to those of nearly allied .species, ujz. : — Lcpisina 

 saccharina. The normal scale is somewhat ovate in shape 

 and is traversed longitudinally by striae which are broken up 

 at the margin of the scale into the familiar cuneate " exclama- 

 tion " markings (see Figure 372). In the case of Lcpisina 



Figure 371. 

 itlatoria agardhii Gom. 



