5'0 



NA TURE 



[March 30, 1899 



If attention be given to the parts printed above in italics, 

 I think it will be admitted that the writer did not consider the 

 yellowness of the reflecting particles as the exclusive cause of the 

 greenness in sea water, and in the last sentence quoted it 

 is stated that the water on the west coast of Scotland, when 

 examined in a long tube, transmitted a blue-green light, there- 

 fore greener than the water of the Mediterranean. 



The paper concludes with some tests made in Loch Lomond 

 and with pure water, and a number of well waters ; these were 

 found to vary from blue to yellow ish brown. As the waters of 

 most of our rivers and lakes are yellowish brown, it is probable 

 that it is the addition of this yellowish water to sea water 

 that makes the seas surrounding our islands of a greenish 

 colour. John Aitken. 



Ardenlea, Falkirk, March 20. 



The Wehnelt Current Interrupter. 



The form of contact breaker recently introduced by Wehne't 

 is attracting so much notice, that it may be worth while to draw 

 attention to an essentially identical arrangement described by 

 Spottiswoode for use with an induction coil, more than twenty 

 years ago (Proc. Koy. Soc, vol. .\.\v. p. 549). lie says: 

 " Another form of contact breaker was also occasionally used. 

 The principle upon which it was based was the sudden disrup- 

 tion of a thin film of conducting liquid by a discharge between 

 the electrodes of a circuit. The mode of eflecting this was to 

 make one electrode terminate in a platinum plate fixed in a 

 horizontal position, and supplied with a uniform film of dilute 

 sulphuric acid ; the other in a platinum point, the distance of 

 which from the plate is capablelof delicate adjustment by means 

 of a screw. Electro-motive force required for this break is not 

 less than that of five cells of Grove. .-Vs soon as the current 

 passes, the fluid between the plate and point will be decomposed, 

 and electrical continuity broken. This done, the fluid flows 

 back again, and continuity is restored. By a proper adjust- 

 ment of the supply of fluid and of the distance between the 

 electrodes (the latter varying from '05 to 'OOI of an inch), the 

 number of disruptions may be made to attain 1000 per second. 

 The currents delivered by this form of break are exceedingly 

 uniform, and the eftects produced are quite equal in delicacy to 

 those produced by the electromagnetic or by the wheel break." 



R. J. Strttt. 



In reference to the Wehnelt current interrupter — in 1874 I 

 used a similar interrupter on a coil with fifty Groves' cells. The 

 idea was not even then new, for although my experiment was 

 due to accidental short-circuiting of electrodes during electrolytic 

 experiments, which led to my final application of the so-called 

 interrupter as a resistance to current, and then as a rapid make- 

 and-break, I found that some of the old masters of electrics had 

 evidently used it before. Since November 1896, I have always 

 endeavoured in using a Jackson tube to condition the tube by 

 heating, when connected with coil, .so that the make-and-break 

 of coil shows infinitesimal sparking and works with such rapid 

 vibrations that a musical note is produced, the pitch varying as 

 the position of the flame heating the tube is altered Shadow- 

 graphs can then be obtained of the human trunk from thirty-five 

 seconds upwards, and the results on English fluorescent screens 

 are almost perfect. This h.is all been mentioned in my lectures 

 at the Royal Artillery Institute, iV:c., the first being at the end of 

 October 1896. William Webster. 



The Laboratory, .\rt Club, lilackheath. 



Palaeolithic Implements from the Valley of the Ver. 



The river Ver rises at Markyate Street, near Dunstable, at 

 the junction of Hertfordshire with Bedfordshire, and runs to St. 

 Albans, whose ancient name \'crulamium is derived from the 

 river. Leaving St. Albans, the river becomes the Colne and 

 joins the Thames at St.aines. Many Paleolithic implements 

 have been found by myself ami others in the valley of the 

 Colne, but up to now none have been recorded from the valley 

 uf the Ver. 



It is true that for many years I have found Pal.-eolithic imple- 

 ments in contorted drift (or where contorted drift has been) on 



NO. 1535, VOL. 59] 



the highest hill-tops north of the source of the Ver, but none of 

 these positions have been in the river's valley. They have 

 belonged to large ponds and swamps of Pal:tolithic age on the 

 hill-iops. 



For the last three or four years small excavations for clay have 

 been made in a brick-yard east of Markyate Cell, but until this 

 last winter I have never seen any human work amongst the 

 excavated material. The implements occur in relaid contorted 

 drift, which has been washed in patches from higher ground, 

 The implementiferous material only occurs here and there in the 

 brick-field ; it is a brown clay full of large stones, and rests upon a 

 brick-earth of much greater age, probably glacial, which in turn 

 rests on Lower Chalk. The implementiferous clay is on the 

 surface, and is never more than two feet deep. The pit is 108 

 feet above the Ver, and 547 feet above the Ordnance datum. Oi> 

 the hills to the north, and removed from the water-shed uf the 

 Ver, implements occur at 595 feet. 



I have lately found six Palceolithic implements in the valley of 

 the \'er at Markyate Street, all above the average in size and 

 weight ; they are faintly ochreous and slightly abraded. The 

 example illustrated to one-half the actual size — 1673 in my 



I 



Pala;olilhic implement from ihe valley of the Ver. One-half actual siic 



collection— weighs i lb. 63 ozs., two others weigh I lb. i oz. 

 each, others i lb 4 ozs. and I lb. 4J ozs. With these implements 

 were numerous large cores and large blocks of flint, from which 

 a flake or two had been struck. These were alxandoned by me 

 as too heavy for convenient carriage. Only one flake has come 

 to hand ; in fact, no stones as small as ordinary flakes are in the 

 material. I have found a few Palnrolithic flakes one and a half 

 miles nearer St. .Vlbans, in the same river valley, north of 

 Friar's Wash. 



Twenty-one years have now passed since I first directed 

 attention to the l'al.t;oIithic implements found on the hill-lops 

 of North Herts [[oKr. Anth. ItistitiiU, vol, viii., iS7S>. Since 

 that time I have greatly extended my observations on these hills, 

 but no evidence w hatever has been seen by me indicative of a 

 greater antiquity than post-glacial. The high-level implements 

 at North Herts and South Beds are never in gkacial material. 

 The implementiferous brick-earth is always on the top of the 

 glacial clay, where the latter is present, and to this rule I 

 have seen no exception. The glacial gravels and clays anil 

 the boulder clay are here positively barren of human work. 



Dunstable. Worthin(;ton G. Smith. 



