March io, 1910] 



NA TURE 



full egg-cases attached to their abdomens. I put several 

 individuals into different aquaria, and was much annoyed 

 -to find that they fell victims to various enemies during the 

 night. A Dytiscus beetle, the presence of which had been 

 forgotten, accounted for four, and four more were 

 apparently devoured by insignificant fresh-water snails. 

 Those, however, that were placed in a tank by themselves 

 are alive and well, and feed on the green algae supplied 

 to them. The males are about \\ inches long, the females 

 rather smaller. 



When the river comes down in flood experience shows 

 that It is time to be on the look-out for zoological curiosi- 

 ties. Perhaps .Apus itself may reappear once more now 

 that Cheirocephalus has shown the way ] 



Eton, March 5. M. D. Hill. 



The Formation of Large Drops of Liquid. 



The following experiment, based on the temperature- 

 density relations between aniline and water, serves to 

 illustrate to an audience the various shapes through which 

 a drop passes in the course of its formation. .\ glass 

 beaker, about 9 inches in height and 4^ inches diameter, 

 is filled to about 7 inches with distilled water, and about 

 80 c.c. of aniline are added. The beaker is then placed 

 on a burner, and the temperature raised until the aniline 

 floats to the surface of the water. On spreading out at 

 the surface the aniline is cooled, thereby becoming denser 

 than the water beneath. A large drop, i inch or more in 

 diameter, then detaches itself from the mass at the surface, 

 the formation being so slow that the altering shapes of 

 the drop, the drawing out of the neck of liquid, and the 

 thinning of the neck in two places may easily be observed. 

 The large, detached drop falls to the bottom of the beaker, 

 and is there re-heated, thereby again becoming lighter than 

 the water, and rising to the surface, when a second drop 

 is formed. By maintaining the temperature about 80° 

 the formation of drops continues indefinitely in the manner 

 described. The slightly pink colour assumed by the aniline 

 enables the experiment to be seen clearly from a consider- 

 able distance, and the many beautiful shapes assumed by 

 the drops lend an added interest to this simple method of 

 demonstrating their formation. Chas. R. Darling. 



City and Guilds Technical College, Finsbury. 



The Fertilising Influence of Sunlight. 



The letters of Mr. and Mrs. Howard antT of Dr. E. J. 

 Russell in recent issues of Nature point to the conclusion 

 ihat the partial sterilisation of the soil improves its fertility. 

 In connection with this subject, I would like to record that 

 the effect of heating the soil has been observed here for 

 some years. It has been the practice to collect all the 

 refuse of the place that cannot be rotted, such as hedge 

 cuttings, tree prunings, &c. These are placed on a vacant 

 space in the kitchen garden and a fire made of them in 



inter. The fire is generally a large one, burning fiercely 



1 day, and the larger branches keeping it going all night. 



In the following summer the site of the fire is well 

 marked. The rows of vegetables where they pass over it 

 are more than a half stronger than at other parts, though 

 they do not keep that proportion to the end of the season. 

 The increased growth seems to be due to the heating of 

 the soil, and not to the large amount of wood ashes left 

 by the fire, as these are either lifted and used as a top 

 dressing for borders where the spade cannot be used, or 

 are spread over the vegetable ground, the site of the fire 

 being generally left quite bare of ashes. 



Ardenlea, Falkirk, March 8. John* .Aitkes. 



MOLES AND MOLEHILLS. 



T IKE that of other common animals, the complete 

 -»— ' life-stor}- of the mole has yet to be written, ex- 

 ceedingly little being- really known. The difficulties 

 of observing the habits of a subterranean dweller of 

 a most retiring disposition are patent but not alto- 

 gether insuperable, and the wonder is that field 

 naturalists have been content to read and take for 

 granted the information handed down for the last 

 century without any attempt to confirm it. 



NO. 2106, VOL. 83] 



During the winter months one cannot help noticing 

 in the open fields here and there a mole-heiap conspicu- 

 ously larger than the rest. This is a male mole's 

 winter habitation, but at present we do not know 

 whether he lives alone or with his wife, or if the 

 female ever constructs these " fortresses," as they are 

 called. Probably he lives alone, and probably females 

 make " fortresses " slightly more simple in construction 

 and smaller in size than those of die males. If we 

 take a spade and carefully slice away the top of a 

 fortress, we shall find several hollow tunnels or runs, 

 which may be opened up and folk)wed to the base of 

 the " fortress," whence they lead away into the field. 

 Slicing further under these into the ' fortress," and 



mhu/S .. 



Fig. I. — Firet stage of the fortress — sectional view, r b, Mole's rua below 

 the surface ; H H," heap of ejected eaith. 



just below the ground-level, we come upon a large cir- 

 cular cavity filled with a bundle of grass or dead 

 leaves; this is the mole's nest in which he sleeps. If 

 he has lately quitted it the interior will be quite warm 

 to the hand; the mole himself, however, will never be 

 caught in the nest. When the nest is removed and 

 the cavity examined, it will be found about a foot in 

 diameter and worn smooth by the mole wriggling 

 about as he wraps his nest round him, for that is his 

 method of arranging himself within it. Two or more 

 tunnels will be found leading away from the nest- 

 cavity into the field. One of these is particularly 

 noteworthy, as it is found in nearly even,- fortress; 



H 



hMhkAif'-^.. 



Fig. 2. — Second stage of the fortress — sectional view, n, Nest-cayity ; 

 B, bolt-run ; h, heap of ejected earth. 



this exit leads from the bottom of the nest perpen- 

 dicularly downward for about a foot, then, turning 

 upwards, it joins another run. Its origin and use 

 are uncertain, but it is usually regarded as a sort of 

 sally port, and is known as the "bolt-run." 



It is extremely unlikely that the mole deliberately 

 selects the site of his fortress, as he is practically 

 blind; probably he sets to work whenever the im- 

 pulse seizes him, and proceeds in the following man- 

 ner. He commences to enlarge a nest-cavity, ejecting 

 the earth which he has loosened with his powerful 

 claws out of a hole in the roof ; this he does with the 

 top of his head in little jerks. The quiet observer may 

 see a sausage-shaped mass of earth issue from below 



