January 14, 1909] 



NATURE 



309 



Magnesium in Water and Rocks. 



The recent publication of analyses of salt in the pans 

 in Cape Colony by Dr. Juritz (dgricultural Journal, 

 November, 1908, Cape Town) brings to a head a problem 

 which has been puzzling me for a long time. A large 

 amount of inagnesia is dissolved in water on the decay 

 of rocks, yet a very small portion finds its way to the 

 sea. Dead coral r'eofs become dolomitised, but, as a 

 general rule, recent limestone deposits do not contain more 

 than 1 per cent, of magnesia ; the magnesia dissolved in 

 ^la-water, therefore, is the accumulation of long ages, and 

 should bear some relation in quantity to that of sodium, 

 vui magnesium in the salts of sea-water is less than one- 

 twelfth that of sodium. In the up-country pans in Cape 

 Colony which collect the water washing over dolerite hills 

 and evaporate the contents on their shallow surfaces, we 

 find plenty of magnesia in the liquors, but practically none 

 in the crystallised product. Here are Dr. Juritz's figures 



Lime sulphate 

 Lime chloiide 

 Magnesium sulphate 

 Magnesium chloride 

 Sodium sulphate 

 Sodium chloride 

 Potassium chloride 



Of the seventy-three samples of salt analysed, all tell 

 the same tale ; one from Belmont Salt Pan, near 

 Kimberley, contains 759 per cent, magnesium sulphate, 

 two contain more than 1-5 per cent., and the rest 1-5 per 

 cent, or under. The ground water, however, struck in 

 wells, is often entirely undrinkable with Epsom salts. 



Magnesia compounds, on the other hand, are con- 

 .^taiitly being drawn down in the earth's crust by the 

 descending surface waters, and cause dolomitisation. The 

 older the limestone, generally speaking, the more it is 

 dolomitised ; joints and bedding planes in limestone are 

 dolomitised when the rest is pure limestone, as in the 

 " dunstone " selvages along Joints in the Carboniferous 

 Limestone of Durham and Northumberland. Why do the 

 magnesia compounds go downwards and not outwards 

 • IS the salts of lime and soda do? 



The same happens with solutions of iron ; practically 

 none reaches the sea, but large amounts descend and re- 

 place limestone by spathic iron or hematite. In this case 

 one would conclude that the earth's magnetic nucleus 

 C'Nerted a pull on the free iron in solution, which, cease- 

 lessly acting, tended to impoverish the surface of iron. Is 

 there some such action going on with regard to magnesia? 

 Taking Farrington's suggestion that the average compo- 

 sition of meteorites represents the average composition of 

 the earth, then the nucleus should contain a very large 

 proportion of magnesium. Is there any evidence for an 

 attraction of magnesium for magnesium when magnetised 

 as there is in the case of iron for iron? 



Ernest H. L. Schwarz. 



Rhodes University College, Grahamstown, Cape 

 of Good Hope, December 21, 1908. 



Phosphorescence on a Scottish Loch. 



A REMARKABLE illumination was observed about eight 

 years ago on a certain part of Loch Bulig (which lies in 

 the north-western boundary of .\berdeenshire). As it 

 appears to be the only known occurrence of phosphor- 

 escence on a Scottish loch, your readers may be interested 

 in it. It appeared in the form of innumerable brilliant 

 lights, shooting rapidly on the surface of the water, but 

 many leaping one or two feet above it. It lasted for about 

 a minute, and was repeated twice at intervals of about 

 ten minutes. The effect was very striking, the brilliance 

 being almost dazzling. It seemed that it could not be 

 accounted for in any other way than by phosphorescent 

 animalcula;, disturbed probably by a shoal of fish which 

 are known to inhabit the loch. 



Inquiry elicited the information that near where the 

 lights were seen a soft bank stretched out from the side 



NO. 2046, VOL. 79] 



towards the centre of the loch. I have been desirous since 

 that time to gather some of the deposit, if possible, for 

 examination, but only a few months ago was I able to 

 carry out my intention. I found it was a matter of no 

 little difficulty, as the loch at that part is about 25 feet 

 deep, and though it is usually quite smooth it sometimes 

 is somewhat rough. The first attempt was a failure, the 

 day being squally, the waves 2 or 3 feet high, and the 

 strong wind and current rendered it difificult to locate the 

 bank and collect specimens. The second attempt, how- 

 ever, was successful, and I found that the bottom was 

 generally stony, but gave place to soft material just above 

 where the lights had beeti seen. I collected two quanti- 

 ties of the deposit, and found that it consisted of sand 

 mi.xed with a large quantity of carbonaceous matter, mostly 

 in the form of small rolls, half an inch to one inch long. 

 Microscopic examination showed that these rolls contained 

 animals encased like tubicolous annelids ; they were quite 

 active, emerging from the tube, grasping black particles, 

 and then retreating ; some were encased in parchment- 

 like tubes, through which the rapid actions of the animal 

 could be distinctly seen ; one was found with a transparent 

 tunic, hanging by a ring from the neck, resembling 

 Oxyethira costalis (Hydrophilideas) ; I still have this speci- 

 men. Along with these and other animals were numerous 

 diatoms, nematodes, &c. As some of these animals belong 

 to classes which are known to be phosphorescent, it seems 

 that their presence in the deposit is sufficient to account 

 for the remarkable appearance seen. This was confirmed 

 by finding that the sand contained much more phosphate 

 tlian sand usually contains ; also, by testing with 

 ammonium molybdate some of the black matter, including 

 one of the black rolls containing an animal, after a few 

 hours a distinct yellow precipitate was found, but only in 

 the vicinity of the black roll. 



I shouM think that this deposit would form an interest- 

 ing preserve for zoologists, and therefore I relate the 

 circumstance, and shall be glad to give any further in- 

 formation to anyone who may desire it. 



Thos. Jamieson. 



Chemical Laboratory, 10 Belmont Street, .Aberdeen. 



[It is to be hoped that Mr. Jamieson will re-observe 

 the interesting phenomenon he saw on Loch Bulig and 

 collect material at the time. If he saw numerous lumin- 

 escent organisms leaping in the air, they may possibly 

 have been Chironomids with phosphorescent bacteria. He 

 gives no convincing evidence in his letter that the 

 organisms collected from the deposit were connected with 

 the " phosphorescent " display. We may recall the fact 

 that a " phosphorescent " Enchytr^id has been reported in 

 Britain. — Ed. N.tTURE.] 



The Movement of Water in Soils. 



In Nature of .August 0, 1908, Dr. Russell refers, in his 

 note on soil moisture, to some information on this subject 

 which I published in Memoir No. 6 (Chemical Series) of 

 the Department of Agriculture in India, and says, " Dr. 

 Leather argues that water moves upwards from a limited 

 depth only. . . . The results are equally well explained on 

 the supposition that the upward movement takes place at 

 all depths, since the amount of water present in a particular 

 layer depends on the respective rates at which water is 

 gained from below and lost to the upper layers." 



I still maintain that the process of upward movement of 

 water through a soil during dry weather is one which is 

 not brought into operation throughout all strata of a soil 

 instantaneously, but that, on the contrary, time is required 

 for it to be communicated through succeeding strata ; con- 

 sequently, during a dry period there will be strata in which 

 the process has not yet become established. Until an 

 alteration of the surface tension occurs in any stratum 

 there can be no movement (due to this cause) of water, 

 and a necessary result of the fact that this alteration of 

 surface tension through succeeding strata is gradual is 

 that any such alteration must be accompanied by a decrease 

 of water per cubic foot. 



A second consequence is that if the total decrease of 

 water which occurs during a dry period throughout the 



