8 



NATURE 



\Nov. 5', 1874 



of greater or less strength, and travelling up the stream with 

 different speeds, take the place of the more gentle undulations. 

 The distinction between ring-vortices and ring-shapei undulations 

 is perhaps here too strongly and improperly overjriwn, as, be- 

 sides the improbability that effects so exaggerated as perfect air- 

 wliirls are really ever attained in ordinary gas-jets, the properties 

 of the undulations that correspond to and lead up to them in 

 ordinary currents must evidently resemble theirs in all respects, 

 so that the deeper and stronger interior undulations move up the 

 jet more rapidly than open and weaker exterior ones on the sur- 

 face ; for it seems probable that both vortices and ring-waves of 

 strongest rarefaction will generally occur nearest to the centre or 

 axis, and those of weakest rarefaction furthest from it, or nearer 

 to the slow-moving outer surface of the jet. The effect of the 

 collision and destruction of a weaker by a stronger ring-wave, 

 when they overtake each other, is the same as that of perfect 

 circulating whirls ; the balance of pressure in one part of the 

 circular wave being broken by a shock, it collapses in every 

 other part, and if both waves are destroyed, the further progress 

 of the jet is intercepted at that point, and it scatters itself in a 

 confused cloud at the point of concourse and disruption of 

 the waves. The long-enduring smoke- or steam-rings often seen 

 projected from the funnels of locomotive engines at starting, or 

 when moving slowly and emitting separate puffs, illustrate appa- 

 rently the mutual action of closely picked parallel jets like those 

 of an ordinary gauze flame ; for the impeded passage to the 

 outer air offered by a number of such surrounding jets, just as by 

 the funnel of the locomotive engine, favours the production of a 

 strong vacuum round the jet-aperture or blast-pipe, .and of a 

 strong wave or steam-ring, the moment that the jet or blast takes 

 a side-swing or a sudden leap upwards that calls the action of the 

 partial vacuum into play. A. S. Hersciiel 



^To be continucJ.) 



A New and Simple Method for making Carbon Cells 

 and Plates for Galvanic Batteries 



■Some time since a correspondent asked for an easy method to 

 construct carbon plates. A paper of mine was read in .Section A 

 at Belfast on the subject, and as it describes a process by which 

 any experimentalist can constnict not only plates but cells of 

 carbon, I have thought a condensed account of the process may 

 be appropriate for your columns. 



With a syrup made of equal quantities of lump-sugar and 

 water, mix wood-charcoal in powder with about a sixth part of 

 a light powder sold by colourmen, called vegetable black. The 

 mixture should hang thickly on any mould dipped into it, and 

 yet be sufficiently fluid to formitsell into a smooth surface. The 

 vegetable black considerably helps in this respect. 



Moulds of the cells required are made of stiff paper, and 

 secured by wax or shellac. A projection should be made on the 

 top of the mould for a connecting piece. These moulds are dijjped 

 into the carbon syrup, so as to cover the outside only, and then 

 allowed to dry. This dipping and drying is repeated until the 

 cells are sufficiently thick. When well dried they are then 

 buried in sand, and baked in an oven sufficiently hot to destroy 

 the paper mould. When cleared from the sand and burnt 

 paper the cells are soaked for some hours in dilute hydrochloric 

 acid, and again well dried, then soaked in sugar syrup. ^Vhen 

 dry they are then packed with sand in an iron box, gradually 

 raised to a white heat and left to cool. Should some of the 

 cells be cracked, they need not be rejected, but covered with 

 paper or plaster and dipped in melted paraffin. 



Rods or plates of carbon can be rolled or pressed out of a 

 similar composition, but made thicker. Carbon thus made will 

 be found ii have a good metallic ring and a brilli.ant fracture. 



Barnstaple, Oct. 26 W. Symons. 



Ingenuity in a Spider 



A SPIDER constructed its web in an angle of my garden, the 

 sides of which were attached by long threads to shrubs at the 

 height of nearly three feet from the gravel path beneath. 

 Being much exposed to the wind, the equinoctial gales of this 

 autumn destroyed the web several times. 



The ingenious spider now adopted the contrivance here repre- 

 sented. It secured a conical fragment of gravel with its larger 

 end upwards, by two cords, one attached to each of its ojiposite 

 tides, to the apex of its wedge-shaped web, and left it suspended 

 as a moveable weight to be opposed to the effect of such gusts 



of air as had destroyed [the webs previously occupying the same 

 situation. 



The spider must have descended to the gravel path for this 

 special object, and, having attached threads to a stone suited to 

 its purpose, must have afterwards raised this by fixing itself upon 

 the web, and pulling the weight up to a height of more than two 

 feet from the ground, where it hung suspended by elastic cords. 

 The excellence of the contrivance is too evident to require fur- 

 ther comment, 



Torquay, Oct. 26 John Toi-aAM 



Note on the Rhynchosaurus Articeps, Owen 



Referring lately to Prof Owen's description of the Rhyn- 

 chosaurus ("Palaeontology," p. 264), first discovered by myself in 

 1S3S-39, in the New Red Sandstone of Grinshill, near Shrews- 

 bury, I remarked that in speaking of the ichnolites supposed to 

 belong to this animal he says there is an " impression corre- 

 sponding with the hinder part of the foot, which reminds one of 

 a hind toe pointing backwards, and which, like the hind toe of 

 some birds, only touched the ground. " In this account nothing 

 is said of any claw being attached to this hind X^k, nor have I 

 met with ary description of a claw in other authors. 1 have there- 

 fore thought it worth while to mention that I possess a specimen 

 from Grinshill that shows distinctly the impression of a straight 

 claw pointing backwards. There is also, on the same slab, the 

 impression of another smaller foot of only three toes with 

 strong straight claws, which has behind it a slight impression 

 corresponding with the hind toe of the larger footprints. It is a 

 curious fact that the claws of tlie larger impression, though larger 

 than those of the smaller footprint, are so much recurved as not 

 to project much beyond the ends of the toes, while on another 

 slab (rom Storeton there are reliefs with both straight and re- 

 curved claws, the latter giving the idea of a foot like that of 

 the Great Anteater. In these .Storeton ichnolites the hind toe 

 exhibits no cliw, nor am I sure whether certain rounded ele- 

 vations represent the sm.aller footprint in the Grinshill specimen. 

 Upon another slab of Storeton stone I have a mark resembling 

 the tail-mark on the slab presented by Mr. Strickland to the 

 Warwickshire Museum, but unfortunately the footmarks con- 

 nected with it are too indistinct to decide its origin. In a third 

 slab from Storeton, besides several impressions with straight 

 claws, there is one three inches long, the second toe of which has 

 a straight claw % in. in length. I h.ave also Cheirotherium foot- 

 prints with long straight claws from the same quarries. 



I have put these few remarks together to fulhl the wish of Prof. 

 Owen " to obtain the means of determining the precise modifi- 

 cations of the locomotive extremities of the Rhynchosaurus." 

 Perhaps by this time this object may have been attained, for at 

 the Congres des Savans at Paris in 1S6S the discovery of two 

 almost perfect skeletons was announced, and drawings of them 

 were exhibited by a professor fro.-n Lyons. 



T. Ogier Ward 



[So far as the photographs can be deciphered, they seem to 

 bear out the writer's statements. — Ed.] 



THE ALPINE CLUB MAP OF SWITZER. 

 LAND* 

 T N Nature, vol. vi. p. 203, we adverted to the non- 

 ■'■ existence of a map of the Alps on a scale sufficiently 

 large for general purposes, and briefly referred to the 

 map which was then being produced under the direction 

 of a committee of the English Alpine Club with the view 

 of supplying the want. This map, though not yet finished, 

 has been recently published. Three sheets are completely 

 finished, but the fourth is still in outline, and will be 

 exchanged for perfect copies when the hill-shading is 

 added. 



We believe this to be, so far as it e.xtends, the most 

 e.xact map of the Alps which has yet appeared, and pro- 

 bably no map of its size has ever been produced in this 

 country with more beautiful workmanship or with greater 



* The Alpine Club Map of Switzerland with parts of the neighbouring 

 countries. EililcJ by R. C. Nichols, F.S.A., F.R.G.S., under the superin- 

 tendence of a Committee of the Alpine C'ub. In four sheets. Scale ^.tto'ijoo' 

 (Stanford, 1874) 



