70 



NATURE 



[July 21, 1910 



LETTERS TO THE EDITOR. 

 [Ihe Editor does not hold himself responsible for opinions 

 expressed by his correspondents. Neither can he undertake 

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

 tnanuscripts intended for this or any other part 0/ Nature. 

 No notice is taken of anonymous communicatiotis.] 



Expeiimental Study of Fulgurites. 



Fulgurites, or the tubes of fused sand which are some- 

 times formed when heavy discharges of hghtning strike on 

 sandy soil, are not common enough to mal^e their study 

 very easy. It has been frequently remarlced that they 

 usually have a spiral or cork-screw form, but, so far as I 

 know, it has not been decided whether or not this is 

 accidental, and whether the direction of rotation of the 

 spiral remains constant in the same fulgurite, or whether 

 it is always the same in the case of various discharges. 

 Through a fortunate accident I recently hit upon a way of 

 extending our knowledge of these curious autographs of 

 thunderbolts. The accident referred to was the circum- 

 stance that I was standing within about 50 feet of the spot 

 on our lawn where a rather heavy discharge struck a day 

 or two ago. I was about to walk across the lawn at the 

 time, but was delayed a moment to reply to a question, 

 when the bolt fell. The report was not deafening, re- 

 sembling the explosion of one of the modern dynamite 

 cannon crackers with which we have become familiar. 

 There was a distinct flash of fire at the surface of the 

 ground, and a column of steam or smoke 6 or 8 feet high. 

 On examining the spot I found three patches of withered 

 clover in a line about 18 inches apart. At the centre of 

 one was a hole about an inch in diameter, and in the 

 neighbouring one a smaller hole ol perhaps a quarter 

 the size. It had been raining hard for a hour or more, and 

 we had had much rain for the past week, which made the 

 ground an excellent conductor, and I was surprised to find 

 that I could pass a straw down the larger hole a con- 

 siderablp distance. 



I mrrll-il :il>uLil 15 lb. of solilrr in an iron pot anil pound 



Photcgraph of th^ 



ground by a lightning 



it into the hole until it was full, and then carefully 

 excavated the cast. In digging it out, I found a lateral 

 tube several inches below the surface joining the two holes, 

 and one or two lateral branches to the large tube, into 

 which the solder had not penetrated. The cast obtained 

 wa« nearly 4 feet in length, and the ground was soaking 

 wet, which surprised me a good deal, for I imagined that 

 the discharge would spread out and become dissipated long 

 before reaching a depth of 4 feet in wet soil. The edges 

 of the tubes were lined with small patches of white grains 

 of sand fused together. The metal cast had an unmistak- 

 able spiral form, which could be followed for its entire 

 length, and was especially conspicuous at the lower or 

 smaller end. The diameter of the artificial fulgurite in- 

 creased to a depth of about 2 feet, after which it diminished 

 gradually. The spiral form can be seen in the accompany- 

 ing photograph of the cast. It was clock-wise in the down- 

 ward direction, that is, it was similar to that of a cork- 

 screw. The surface was covered with small buds, which 

 were arranged in straight lines along its length, some of 

 the lines 7 or 8 inches long. One of these lines can be 

 seen m the photograph immediately to the right of the 

 label. These lines may be due to cracks in the tube, result- 

 ing from the explosive action of the steam. The localisa- 

 tion of a bright light at the surface of the ground is 

 extremely interesting. Several members of my family, who 

 wf>re not looking at the spot at the moment the flash struck, 

 turned round at the report, and said that thev saw a 

 bright light and a cloud of smoke. It will be interesting 

 NO. 2125, VOL. 84] 



to hear if others have noticed this phenomenon. It may pos- 

 sibly be due to the combustion of a blast of gas generated 

 by the passage of the discharge through the soil. 



On the day after the storm I found another and 

 much larger hole on the golf links, where a very heavy 

 discharge had struck and demolished a wooden bo.\ of 

 sand on the top of a banked-up tee, leaving no mark, 

 however, on an iron cylindrical can of water standing 

 beside and in contact with the sand box. Lateral branches 

 had spread out in all directions over the top of the tee, 

 making furrows similar to mole tunnels. I have not yet 

 made a cast of this hole, which is probably 6 or 8 feet 

 deep, pending the decision of the golf committee. Similar 

 holes must be of very frequent occurrence, and their study 

 liy this method should prove interesting. 



East Hampton, Long Island. R. W. Wood. 



Ooze and lirigation. 



The valuable contribution to this subject contained in the 

 letter of Mr. Horwood (July 14, p. 40) shows the import- 

 ance of communicating the results of research. I am, in 

 consequence, submitting a few further facts which have 

 not heretofore been made public. Up till the present time 

 it has been assumed that our British Annelids were limited 

 to a few species of earthworms, and a few aquatic forms 

 usually lumped together as Tubifex. So far is this from 

 being the case that we have at least four distinct groups 

 of indigenous worms, to say nothing of the many foreign 

 species found at Kew, Chelsea, Oxford, and elsewhere. 

 These are, first, the true earthw-orms, of which we have 

 nearly forty species, now ranged under upwards of half a 

 dozen genera. Secondly, certain species of semiaquatic 

 worms, including not only the well-known Allurus 

 (Eiseniella), but two species of Helodrilus. Of these, H. 

 oculatus, Hoffmeister, is now known to be British, while a 

 second species, H. clcngatus. Friend, new to science, is at 

 present known to occur in Cornwall in streams and lily 

 ponds. These are of peculiar interest, both because they 

 necessitate a revision of nomenclature and because they 

 link on tlie earthworms with the aquatic forms. 



Next come the ooze formers, which, 

 are exceedingly numerous, and occur in 

 almost all our lakes and ponds, our 

 livers, streams, ditches, and pools, 

 doing an immense work as scavengers 

 ;ind inould-makers. Lastly, we have 

 to notice another series, which may 

 be conveniently spoken of as white 

 worms, (Enchytra?ids). It is in rela- 

 discharge. tion to these that I wish especially to 



make one or two observations. Some 

 years ago 1 carefully examined the banks of the Eden 

 near Carlisle. I then found, not only a large series of 

 water worms engaged in making ooze, but, at particular 

 seasons of the year, an equally varied assortment of 

 Enchytraeids (Fridericia, Heulea, Enchytrajus, and others) 

 at the roots of grasses. By careful observation I found 

 that these were most abundant at the time when decaying 

 vegetable matter was in a state of fermentation, and that 

 they were apparently engaged in clearing off this fermenting 

 matter. 



I have recently further observed on the Malvern Hills 

 that, if the stones are lifted which have for a time been 

 covering the grass and causing it to decay, one finds that, 

 when a given stage of decay is reached, certain white 

 worms always make their appearance ; and that these 

 Enchytraeids are, curiously enough, almost invariably 

 associated with a species of earthworm (Luiyibricus rubellus, 

 Hoffm.). Other observations, such as that relating to the 

 amphibious nature of the tiny aster-worm (Enchytraeus 

 parviilus, Friend), and the action of other forms on decay- 

 ing seaweed and the like, will call for fuller treatment 

 elsewhere. Enough has been said to show that a very wide 

 field of observation is opened up, and that, w'hile it has its 

 interests for the geologist, it is of supreme importance for 

 the biologist and the student of agriculture. I am at 

 present engaged in a series of observations which are 

 bringing many new facts to light. 



HiLDERic Friend. 

 Malvern. July 18. 



