NA TURE 



\_March 24, 1887 



have made in my travels of a zone of almost perpetual electrical 

 discharge in the belt of the " doldrums " all round the world. 



Anywhere in that belt, a more or less intermittent display of 

 sheet lightning commences the moment the twilight of sunset 

 has sufficiently faded away, and continues with varying intensity 

 till the light of morning prevents further observation. 



The localisation of this belt of lightning is very obvious as 

 we run a section across the equator on board ship. There is 

 very little electrical discharge in the high-pressure belt of anti- 

 cyclones which encircle the earth approximately under the lines 

 of the tropics ; but as we approach the low-pressure band of the 

 " doldrums," where the two trade-winds, or the two monsoons 

 meet, then the display of lightning is of nightly occurrence, 

 even if there are no actual thunderstorms. 



This electric discharge has a diurnal period like every other 

 meteorological element ; for night after night, as I have slept on 

 deck in Malaysia during the change of the monsoons, I have 

 noticed a very marked diminution of the lightning after I or 2 

 a.m. If a total eclipse of the sun could last for twelve hours, I 

 have no doubt that we should see more or less lightning all the 

 time, with a regular set of diurnal variations. 



Edlung and others have noticed the gradual decrease in the 

 frequency of thunderstorms as we recede from the equator ; but 

 I wish to show now, not only that the discharge is of nightly oc- 

 currence, but that the locality of maximum effect is not so much 

 on the equator as in the "doldrums." The sheet lightning 

 may be the reflection of distant thunderstorms, or it may be the 

 silent discharge of electricity. Meteorologists are much divided 

 as to the possibility of the latter ; but it is certain that the 

 amount of sheet lightning is out of all proportion to the fre- 

 quency of actual thunderstorms. 



Is it not possible that we may find in this perpetual lightning, 

 some clue to the origin of earth- currents everywhere? and in the 

 diurnal variation in the discharge, some probable reason for the 

 hourly variation of the aurora, and of some magnetic elements ? 

 No doubt it is at present difficult to connect the electricity of 

 lightning with the electro-magnetic effects of terrestrial magnet- 

 ism or the aurora ; and though Edlung's theory is defective in 

 this respect, I cannot help thinking that he is right in collating 

 thunderstorms on the equator with the glow discharge of elec- 

 tricity on the Arctic circle ; and it is in the hope that the dis- 

 covery of the constancy of electrical discharge in the "doldrums " 

 may perhaps assist in the evolution of a true theory of the aurora, 

 that I have penned this short notice. 



Ralph Abercromby 



21 Chapel Street, London, March 15 



Scorpion Virus 



Proi'. Bourne's experiments, related in the Proceedings of 

 the Royal Society of January 6, 1887, seem to establish the fact 

 that although the scorpion may be provoked to strike and wound 

 itself or another scorpion, it is incapable, in either case, of causing 

 any toxic action, however active the virus may prove in respect 

 of other creatures. That it is, in short, with the scorpion as it 

 is with the cobra or viper : they poison other creatures, but not 

 themselves or each other. 



Some years ago an exhaustive series of experiments brought 

 me to the conclusion that a cobra is not poisoned by cobra virus, 

 whether inoculated by its own fangs, by those of another cobra, 

 or by a hypodermic syringe. The same in the case of daboia 

 and other viperine snakes. 



It seemed, however, that the bungarus, a less deadly snake 

 than the cobra, occasionally is aflected, though slowly, by the 

 cobra virus, but that it escapes more frequently than it suffers; and 

 when it does suffer the effect of the poison is greatly diminished. 

 On the other hand, non-venomous snakes, lizards, frogs, fish, 

 moUusca, and other low forms of life, all rapidly succumb to 

 snake poison. 



The details of these experiments are to be found in the 

 " Thanatophidia of India," published in 1872, and in referring to 

 them Prof. Bourne remarks : "They show conclusively that the 

 cobra poison will not affect a cobra, and will not even affect the 

 viperine jnyas." I would correct the latter part of the quota- 

 tion so far as to say that the ptyas is a colubrine harmless 

 snake, not a viperine snake, and that it rapidly succumbs to the 

 cobra virus. 



Prof. Bourne has helped to dispel another of the popular 

 delusions which cling round venomous creatures. 



March 14 J. Fayrek 



THE RELATION OF TABASHEER TO 

 MINERAL SUBSTANCES 

 lyrR. THISELTON DYER has rendered a great 

 •'■'•'- service, not only to botanists, but also to physicists 

 and mineralogists, by recalling attention to the very inter- 

 esting substance known as " tabasheer " (Nature, vol. 

 xxxv. p. 396). As he truly states, very little fresh informa- 

 tion has been published on the subject during recent 

 years, a circumstance for which I can only account by the 

 fact that botanists may justly feel some doubt as to 

 whether it belongs to the vegetable kingdom, while min- 

 eralogists seem to have equal ground for hesitation in 

 accepting it as a member of the mineral kingdom. 



It is very interesting to hear that so able a physiologist 

 as Prof. Cohn intends to investigate the conditions under 

 which living plants separate this substance from their 

 tissues. That unicellular Alga;, like the Diatomaceas, 

 living in a medium which may contain only one part in 

 10,000 by weight of dissolved silica, or even less than 

 that amount, should be able to separate this substance to 

 form their exquisitely ornamented frustules is one of the 

 most striking facts in natural history, whether we regard 

 it in its physiological or its chemical aspects. 

 I Sir David Brewster long ago pointed out the remark- 

 able physical characters presented by the curious product 

 of the vegetable world known as " tabasheer," though so 

 far as I can find out it has not in recent years received 

 that attention from physicists which the experiments and 

 observations of the great Scotch philosopher show it to 

 be worthy of. 



Tabasheer seems to stand in the same relation to 

 the mineral kingdom as do ambers and pearls. It is 

 in fact an opal formed under somewhat remarkable 

 and anomalous conditions which we are able to study ; 

 and in this aspect 1 have for some time past been 

 devoting a considerable amount of attention to the minute 

 structure of the substance by making thin sections and 

 examining them under the microscope. It may be as 

 well, perhaps, to give a short sketch of the information 

 upon the subject which I have up to the present time 

 been able to obtain, and in this way to call attention to 

 points upon which further research seems to be neces- 

 sary. 



From time immemorial tabasheer has enjoyed a very 

 high reputation in Eastern countries as a drug. Its sup- 

 posed medicinal virtues, like those of the fossil teeth of 

 China and the belemnites (" thunderbolts ") of this 

 country, seem to have been suggested by the peculiarity of 

 its mode of occurrence. A knowledge of the substance was 

 introduced into Western Europe by the Arabian physicians, 

 and the name by which the substance is generally known 

 is said to be of Arabic origin. Much of the material 

 which under the naine of " tabasheer " finds its way to 

 Syria and Turkey is said, however, to be fictitious or 

 adulterated. 



In 178S Dr. Patrick Russell, F.R.S., then resident at 

 Vizagapatam, wrote a letter to Sir Joseph Banks in which 

 he gave an account of all the facts which he had been 

 able to collect with respect to this curious substance and 

 its mode of occurrence, and his interesting letter was 

 published in the Philosophical Transactions for 1790 

 (vol. Ixxx. p. 273). 



Tabasheer is said to be sometimes found among the 

 ashes of bamboos that have been set on fire (by mutual 

 friction ?j. Ordinarily, however, it is sought for by split- 

 ting open those bamboo stems which give a rattling sound 

 when shaken. Such rattling sounds do not, however, afford 

 infallible criteria as to the presence or absence of taba- 

 sheer in a bamboo, for where the quantity is small it is 

 often found to be closely adherent to the bottom and sides 

 of the cavity. Tabasheer is by no means found in all 

 stems or in all joints of the same stem of the bamboos. 

 Whether certain species produce it in greater abundance 

 than others, and what is the influence of soil, situation, 



