Feb. II, 1875] 



NATURE 



28s 



would be a considerable thickness of Oolitic strata over the 

 Palxozoics ; but a boring there proved the carboniferous lime- 

 stone at 59 feet from the surface. 



It is generally conceded ihat if the sole object of the explora- 

 tion were to search for coal measures under the south-east of 

 England, it might have been advisable to bore more to the norlh 

 or north-east. There is no doubt that the Oolitic strata is thin 

 in that direction, so that a boring between Maidstone and Folkes- 

 tone would probably not meet with any, or with only a small 

 thickness. But, on the other hand, the Lower Cretaceous strata 

 might there be thick. Borings for water at I*daidstone have been 

 carried to 600 feet below sea-level, and only just pierced the 

 Weald clay, getting water from the top beds of the Ilasiiugs 

 sands. A boring at Ashford, carried to about the same 

 depth, seems to have got into the H.astings sand series ; 

 but how much more Wealden strata may be below either 

 of these bore-holes we cannot tell. Prof. Prestwich sup- 

 poses that the Pala20zoics may lie at a more moderate depth 

 below the sea-lcvel at Folkestone ; and he proposes that the 

 Channel Tunnel should be carried through these old rocks. We 

 must all hope, and I for one believe, that the Tunnel can be suc- 

 cessluUy carried through the chalk ; but if this should fail, it is 

 probable that borings will be made to test the feasibility of Prof. 

 Prestwich's scheme. Meanwhile, the Sub- Wealden Exploration 

 can apply it? funds in investigating other districts. 



It should be remembered that the boring has been mainly sup- 

 ported by landowners and others connected with Sussex. Mr. 

 WiUett, the indefatigable secretary, has worked at the task that 

 Sussex may have the honour of Laduig in an exploration which 

 in future years, whatever may be the success of the present 

 boring, will certainly be extended to other districts in the south- 

 east of England. It is certain that no other spot in Sussex is 

 so well suited for the work ; and, all things considered, the best 

 plan is to begin again on the same site. 



The Committee has always kept the coal question in the back- 

 ground, preferring to urge forward the work on its scientific 

 merits. Still, it is true that the chief cause of the wide interest 

 taken in the boring is the hope that coal will be found, or at 

 least that valuable information bearing on the point will be 

 obtained. It may then be well again to call attention to the fact 

 that Prof. Gosselet, whose researches on the Coal Measures of 

 Northern France are so well known, believes that the boring 

 is in the right position, and that it is very probable that a line of 

 productive coal measures underlies the Weald. He has shown 

 that the coal beds of Hardinghen, in the Boulonnais, are really 

 true coal measures faulted down, and are not an abnormal deve- 

 lopment of the limestone series ; a conclusion with which other 

 geologists now agree. 



I have entered irito these long explanations from a fear lest 

 Mr. Blake's well-meaning criticisms may convey the impression 

 that money is now to be spent at Netherfield which could be 

 better spent elsewhere. I think this is not the case, and I hope 

 that those who have the means and the will may see the import- 

 ance of aiding the work with their contributions. Mr. H. 

 Willett (Arnold House, Brighton) has made himself personally 

 responsilile for the amount (600/.) needed to carry the new boring 

 down to 1,000 feet, trusting that subscriptions will steadily come 

 in for the future as they have done in the past. 



Geological Survey Office, Jermyn Street, AV. Toi'LEY 



London, Feb. 7 



Gaussian Constants 



Prof. Humphrey Lloyd says, in his book " On Magnet- 

 ism," published about two months ago, and reviewed (vol. xi. 

 p. 221) in Nature by Prof. Balfour .Stewart, on page 115, in a 

 paragraph on " Gauss's Theory " : — " In addition to this, mainly 

 through the exertions of General Sabine, magnetic.al obser- 

 vations have been vastly multiplied at other points of the earth's 

 surface ; and the time has consequently arrived when a re-calcu- 

 lation of the Gaussian constants, as they are called, may with 

 advantage be undertaken. This laborious work is now in pro- 

 gress. General Sabine has completed the co-ordin.ation of the 

 observations , and Prof. Adams has generously offered to devote 

 his valuable time to the re-calculation based upon them. The 

 scientific world may therefore, before long, expect to see a series 

 of charts exhibiting the actual condition of the earth's magnet- 

 ism greatly more exact than any which have been yet produced." 



It may therefore interest Prof. Lloyd and others to hear that 



about nine months ago was edited and published at Berlin, at 

 the request of the Imperial Admiralty, "Die Grundlagen der 

 Gaussischen Theorie und die Erscheinungen des Erdmagnetisraus 

 im Jahre 1829, mit Beriicksichtiguug der Srecidarvariationen 

 aus alien vorliegenden Beobachtungen berechnct und dargestellt, 

 von A. Erman und II. Petersen;" a re-calculation of the 

 " Gaussian Constants," based on a co-ordination of the most 

 reliable observalions, containing a series of charts which exhibit 

 the actual condition of the earth's magnetism. 



O. Reiciienbach 



Columnar Formation in Mud Banks 



In reference to the report in Nature, vol. xi. p. 258, on Mr. 

 Mallet's communication to the Royal Society, respecting the 

 hexagonal crystallisation of liasalt, I beg to offer to your readers 

 a similar explarjation of the columnar formation in some mud 

 banks on the shores of some of the rivers in South Africa. 



The modern channels are gradually becoming lower than 

 formerly, owing to the rising of the land, and so the streams in 

 estuaries and reaches have cut out deeper courses in the pre- 

 viously formed muddy bottoms, and these are now exposed on 

 the sides of the rivers, but at the bottom of the valleys, to the 

 action of the sun and the hot winds. These strata of mud are 

 very thick, and they begin to dry on the surface, and split across 

 into hexag.maMiUe discs all over the flat, and this splilting,on the 

 surface gradually deepens into the stratum, and a mass or con- 

 geries of columns is thus formed on the side lying nearest the 

 river. The diame'.er of these columns may vary from 4109 

 inches, but their length is very uncertain, and might be from 

 I to 3 feet. These again become detached by gravity, rains and 

 winds, and tumble into the stream, and are borne away by the 

 currents to the sea, to become imbedded and fossilised in some 

 sand-bank, and probably the study of some future palteonto- 

 logist. 



In the case of basalt the agency of crystallisation is stated to 

 be by Mr. Mallet the abstraction of heat and contraction of 

 fluidity into solidity ; but in this case it may be attributed to 

 loss of moisture by heat and dryness producing contraction of 

 fluidity into solidity. A similar result would therefore appear 

 to be produced by apparently two opposite causes, cooling in 

 the one case and heating in the other, but both have tended to 

 produce a closer aggregation of the molecules, and brought 

 them within the range of their peculiar physical affinities. 



Edinburgh J. W. Black 



Floweis and Bees 

 With reference to a letter which appeared in Nature, 

 vol. xi. p. 24S, I may mention that on the 30th of August last 

 nearly all the Snapdragon flowers I could find (including many 

 unopened buds) had been bitten through by bees. I had been 

 looking out for flowers in this state a short time before (I think 

 not more than a week), when I could find only two, and those 

 looked as if they might have been accidentally injured. The 

 quickness and thoroughness with which the work h.ad been done 

 was very striking. C. A. M. 



Iron Pyrites 



I.\ Nature, vol. xi.p. 249, Mr. Carr mentions the fact that some 

 iron pyrites in the Maidstone Museum "have crumbled into a 

 coarse, finely divided mass;" and he inquires whether "such a 

 thing has ever been observed befL.re." It is a very common and 

 well-known fact, and any work on chemistry will explain it. Per- 

 haps we can best answer the question by quoting Ur. Miller on the 

 subject (Chemistry, p. 5SS) : — "Some varieties of iron pyrites, 

 especially those found in tlie Tertiary strata, are speedily decom- 

 posed by exposure to air ; oxygen is absorbed, and ferrous sul- 

 phate formed. This decomposition occurs with greater facility 

 if the disulphide be mixed with other subst.inces, as is the case 

 in the aluminous schists ; in which, by the further action of air, a 

 basic ferric sulphate is formed, whdst the liberated sulphuric 

 acid reacts upon the alumina, magnesia, or lime of the soil, and 

 fi.>nns sulphates ; those of aluminium and magnesia may be ex- 

 tracted by lixiviation. The ordinary crystallised pyrites from 

 the older strata is not thus decomposed, but a variety of a 

 whiter colour is disintegrated rapidly by exposure to the 

 weather; this form of pyrites is known as Marccisitc, ox while 

 lion pyrites." R, 



