SCIENTIFIC NE^AAS. 



[May II, 1 888. 



that the curvature of the earth hides the original flash 

 trom the observer. Dr. Tyndall, while staying at Bel 

 Alp, frequently observed sheet lightning on the horizon, 

 and found, on telegraphing to the Monte Generoso Hotel, 

 that terrific storms were raging over Northern Italy, and 

 that he was merely seeing the reflection in the sky. 



Another form, known as globular lightning, is sometimes 

 seen, but as yet the conditions necessary for its produc- 

 tion are not known. This form of lightning lasts for a 

 much longer period than the others. 



There is also a form of lightning known as the brush 

 discharge, or St. Elmo's fire, which is sometimes seen at 

 sea in lambent blue flames at the ends of the yards and 

 at the mast-heads of vessels. It is also seen occasionally 

 in the Alps, and pine forests have been known to have 

 each little fir-needle tipped with a small lambent light, 

 producing a weird and beautiful effect. 



The colour of the flash depends upon the height and 

 density of the air through which the discharge takes 

 place ; if in the upper strata of the atmosphere, the light 

 is of a bluish colour; if through a stratum ladened with 

 water vapour, the light is of a redder tint ; and if the flash 

 takes place through the denser strata of the atmosphere, 

 the fight is white and intensely vivid. 



The discharge has a considerable effect upon the 

 atmosphere ; water vapour is decomposed, and some of 

 the liberated hydrogen unites with the nitrogen in the 

 air, forming ammonia, small quantities of the oxides of 

 nitrogen are also produced, and in the immediate 

 vicinity of a flash a pecuhar phosphorus-like odour is 

 noticeable, due to the conversion of a little oxygen into 

 ozone. 



It would be very interesting if photographs of the 

 same flash could be obtained from several stations, and 

 the Royal Meteorological Society last year invited photo- 

 graphers to assist them in doing so. Durir.g the violent 

 storm we had last August a number of photographs 

 were taken, but owing to the frequency of the flashes 

 and the very short intervals which elapsed between 

 them, they could not be accurately identified. We trust, 

 however, that further attempts will be made to photo- 

 graph as many lightning flashes as possible, and that 

 they may be sent to the Society with a careful record of 

 the direction in which the camera was pointed, as well 

 as the exact time at which the flash occurred. 



BOULDERS IN COAL SEAMS. 



' I ^HE occurrence of boulders — rounded and water-worn 

 -*■ portions of rock, carried often far from their 

 probable origin, and deposited among strata of a very 

 different character — is no uncommon geological pheno- 

 menon, nor in many cases is their presence difficult to 

 account for. They have been brought by floods, or 

 deposited by glaciers or icebergs travelling over the 

 spots where they are found. But there are instances of 

 boulders to which none of these explanations will fairly 

 apply. Thus in a recent number of the transactions of 

 the Manchester Geological Society (vol. xix., part 1 6, p. 

 404) we find an account of two boulders found fixed in 

 a seam of coal about six inches from its bottom. Both 

 were evidently water-worn, and were not at all like any 

 of the surrounding strata. 



These boulders were found in the Brookside Colliery, 

 near Leigh, in Lancashire. Similar stones have been 



found in coal-seams at Patricroft, Pendleton, Kearsle}-, 

 in the Astley Pit, Dukinfield, in Cheshire, varying in 

 size from a few ounces up to 16 cwt. 



Others very similar in character have been found in 

 other parts of England, in the coal-beds of Saxony, Upper 

 Silesia, Austrian Silesia, and in similar formations in the 

 state of Ohio. 



But the important question is how they can have been 

 deposited as we find them ? The beds of coal and shales 

 in which they are embedded point to slow, gradual 

 processes, going on probably for thousands of years. 

 The boulders, on the other hand, must have been trans- 

 ported by some sudden violent agency. Now how do 

 these facts agree together ? Whatever power would be 

 capable of bringing along these heavy stones would surely 

 have been sufficient, and more than sufficient, to have 

 disturbed and swept away the coal, which was in the 

 process of formation below, and around, and in many 

 cases also above these erratic masses. Yet there is 

 nothing to show that the quiet formation of the coal had 

 been in the least interrupted. If we suppose the boulders 

 to have been brought by a flood, the sudden bursting of a 

 lake, or the irruption of the sea in case of a sudden 

 subsidence, what must have become of the coal ? Water- 

 worn they certainly are, but this may have been in all 

 probability effected long previous to their deposition. It 

 is to be noted that in most cases they are not 

 accompanied by any other matter such as storms and 

 floods would be likely to convey. 



As regards the supposition that they have been 

 brought by ice, we must remember that none of these 

 stones show the slightest signs of glaciation — that is, 

 none of the lines and scratches such as those seen on 

 boulders from the glacial drift. 



Among the hypotheses brought forward to account for 

 their position, one is that they are not bouWers at all, 

 but concretions or aggregations, nodules in fact, formed 

 where they lie. This view, however, in the opinion of 

 an eminent geologist, is disposed of by the fact that some 

 of them are not rounded, but angular, and, furtl"'.cr, by 

 their agreement in structure and composition with rocks 

 from which they have probably come. 



Another supposition is that after carbonaceous matter 

 had been deposited, but not yet consolidated as it is 

 now found, it may have been submerged, and that stones 

 floated by masses of drift-wood and entangled in the roots 

 of trees may have "been dropped through the water, 

 quietly down upon the submerged vegetation at the 

 bottom." 



From the wide divergence of opinions and the absence 

 of any theory which fully meets all the requirements of 

 the case, it is evident that these boulders in the coal- 

 seams require much further study. 



Improved Paste. — The following is a German formula 

 for making a liquid paste or glue from starch and acid. 

 Place five pounds of potato starch in six pounds of water, 

 and add a quarter of a pound of pure nitric acid. Keep it 

 in a warm place, stirring frequently for forty-eight hours. 

 Then boil the mixture until it forms a thick and translucent 

 substance. Dilute with water if necessary, and filter 

 througli a thick cloth. Another paste is made from sugar 

 and gum arable. Dissolve five pounds of gum arabic, and 

 one pound of sugar in five pounds of water, add one ounce 

 of nitric acid and heat to boihng ; then mix the above with 

 the starch paste. The resultant paste is liquid, does not 

 mould, and dries on paper with a gloss. It is useful for 

 labels, wTappers, and fine bookbinders' use. 



