l82 



NA TURE 



[June 20, 1895 



supposed Roman Mithneum or Milhraic temple discovered on 

 the east bank of the river Medway at Wouldham, near Maid- 

 stone. The temple, or " cave," was found by workmen while 

 engaged in remo\nng sand for ballast, and excavated under the 

 superintendence of the exhibitor. It had api^arcntly been built 

 into the Ixink, standing east and west, measuring 40 feet in 

 length and 20 feet in width. Numerous fragments of tiles, 

 samian and other ix)tteiy, animal bones, and a coin of Constan- 

 tinopolis were found in the filling, but no statuarj- or inscriptions. 

 So far this "cave'" is the only one found south of the river 

 Tyne. 



Mr. G. F. Scoit Elliot had on view photographs and objects 

 illustrating his recent expedition to Ruwenzori. The photographs 

 showed characteristic trees and shrubs of Tarn, view of Kagera 

 River, and of Ruwenzori. The objects consisted ol Wandorobbo 

 costume, sword, quiver, fire-stick, and arrows ; Uganda pottery, 

 bark cloths, &c. ; banana meal, &c., in form, ready for export. 



Mrs. Ellis Rowan exhibited Australian wild flowers in water- 

 colours. The examples were from Northern Queensland and 

 Western .Australia. 



A letter and original manuscrifit of Emin Pasha's last 

 Omithok^ical Journal formed an interesting exhibit by Sir 

 William H. Flower. The objects were found by the officers of 

 the Congo Free Slate, after Emin had been murdered by the 

 Arabs at Kinena, on or about October 28, 1892. 



A series of cultures of various forms of the bacteria which 

 had Ijeen isolated from the river Thames, and then cultivated 

 by the methcKls employed in the laboratory, formed Prof. 

 Marshall Ward's exhibit. The bacteria were grouped in sections 

 corresixinding to the different types, and characterised by 

 differences as to the pigment-production, temperature of growth, 

 Capacity of forming spores, behaviour in different media, sizes, 

 shapes, and power of movement, &c. Some of them l>elonged 

 to common species ; others were rare, or unknown, and not 

 classified. 



.\n instrument for describing parabolas by means of a com- 

 bined sliding and link motion was exhibited by the inventor, 

 Mr. II. Thomson Lyon. 



Sir David Salomons showed new forms of "lop" slides for 

 the lantern, selenile and hot-water slide heated electrically ; and 

 illustrated the behaviour of aglow lamp in (he magnetic field, S:c. 



.Mr. F. Knock exhibited a living aquatic hymenopterous 

 insect, Polyncma iialans (I,ubt>ock), Caraphractus liiiclus 

 ( I laliday), described by him in these columns a few w eeks ago. 

 This minute and most Ixjautiful llymenopteron w,-is observed by 

 Sir John Lublnick swimming or flying under water, crawling 

 alxjut weed, \c. The Mymarida (llal.) all oviposit in the 

 eggs of other insects ; Polyntiiia nataits, according to Ganin, 

 having lieen bred from eggs of a dragon fly, yEsihiia. The 

 smallest of this family, Campioptcra papavcris, is but one eighty- 

 fifth of an inch in length. 



The bone structure in the dentary lx)ne of Gomphognalhus, a 

 South .African reptile, was illustrated by one of Prof. Seeley's 

 exhibil.s. The Ijone structure in this fossil, which is of I'ermian 

 age, is not distinguishable from the iKmeslnicturcof a mammal, 

 in the arrangement of the haversian canals and the lacuna-. 

 IVof. Seeley also showed vertical sections through the 

 maxillary and mandibular teeth from the same skull. This 

 exhibit consisted of three vertical .sections of the skull of 

 Gomphognathus taken at the hinder termination of the hard 

 imlale, showing the conical fonns of the single roots to the 

 molar teeth, the flat transverse crowns to the teelh, and the 

 way in which the mandilnil.ar teeth arc opposed to those in the 

 skull. 



A sacred l>onc-lrumpet, drum, and flute were exhibited 

 by Dr. George llarley. The trumpet and tom-t<mi drum were 

 from the temple of a Uuddhi.st monastery in Thibet. They 

 were made from the liones of priests—from their being sup|>osed 

 to tic more religiously effectual. The lruin|>el when lilown 

 emits a rising and falling mournful wailing sound. The drum, 

 „),..„ ,1,. 1 , , I ,i|;irhed to its strings are rattled against the 

 -'• reealile harsh noise which is thought to drive 



ill of the temple. The flute is a Carib Indian's, 



from tfUiaiui, made from the tibia uf a ileer (Coasstii nifiiiin). 

 From it ••an 1»' got the notes I, 2, and 3, in the natural 

 harmot/ ' (1, 7, and S, as in the French flageolet. 



Thi ! hiliits, with demonstrations by means of the 



electrii i 'k place in the meeting-room of the Stwiety. 



I.juitcm slides, illustrating the ethnography of Hritish New 

 Guinea, liy Prof. A. C. Iladdon. The slides illustrated 



the physical characters of different tribes inhabitii^ British 

 New Guinea, some of the occui>ations of the people, several 

 kinds of dances, and the distribution of dance-m.a.-iks. A 

 scries of dwellings from one end of the Protectorate to 

 the other was shown, and two types of canoes. Finally, 

 illustrations of the decorative art of various districts were 

 thrown upon the .screen. Evidence was given in support 

 of the view that British New Guinea is inhabited by true dark 

 Papuans, and by two distinct lighter Melanesian peoples, one of 

 whom may have come from the New Hebrides, and the other 

 from the Solomon Islands. 



Dr. J. Joly exhibited examples of colour photograjJiy, and 

 described his method of obtaining them. The photographs were 

 a realisation ol composite heliochromy in a single im;ige. The 

 method of composite heliochromy requires three images super- 

 imposed by projection. In Dr. Joly's photographs the colour 

 analysis and synthesis are carrietl out in the one image. The 

 colours are the natural colours as they registered themselves U(X)n 

 the plate, and in no case altered after reproduction, lite s|)eci- 

 mens shown were first attempts, produced with rough apparatus. 

 The images showed a slightly grained appearance, but this is 

 avoidable with proper appliances. The process of taking and 

 reproducing the phott^tgraplis tlifters in no way from iirdinary 

 photography \x\K>n the dry plate, save that the sensitive pU»te is 

 exposed in the camera behind a screen lined in jxirticularc-oloiu's. 

 The positive is subsequently viewetl through a screen lined with 

 three other colours; the three "fundamental colours,' which 

 upon the three-colour theory of vision are supposed to give rise 

 to all our colour sensations. 



ON THE TEMPERATURE VARIATION OF 

 THE THERMAL CONDUCTIVITY OF ROCKS> 



§ I. 'T'llE experiments described in this communicatioit 

 were undertaken for the purpose of finding 

 lem|>erature variation of thermal conductivity of some of the 

 more important rocks of the earth's crust. 



§ 2. The method which we adopted w:is to measure, by aid 

 of thermoelectric junctions, the lemiKraiurcs at dift'erenl points 

 of a flux line in a solid, kept unequally heated by sources 

 (positive and negative) applied to its surface, and maintained 

 uniform for a suthcienlly long lime to cause the temperature lo- 

 be as nearly constant at every |)oint as we could arrange for. 

 The shape of the .solid and the thermal sources were arranged to 

 cause the flux lines to be, .as nearly as possible, parallel straight 

 lines ; so that, according to Fourier's elementary theory and 

 definition of thermal conductivity, we .should have 



/■ (M, B )_[f'(M) -5'(T)]-hMT 

 "/•(T, M)~[f(B) - f(M)]-^B.M ' 



where T, .\l, B denote three points in a stream line (respectively 

 next to the top, at the middle, and iiexl to the bottom in the 

 slabs and columns which we used); ;(T), r'(M), :(li) denote 

 the steady temperatures at these ]X)ints ; and .<-(T, M), ^(M, B), 

 the mean conductivities lietween T and M, and between M and 

 B respectively. 



§ 3. The rock ex]x;rimented on in each case consisted of two- 

 equal and similar rectangular pieces, pressed with similar faces 

 together. In ime of these faces three straight parallel grooves 

 are cut, just deep enough to allow the thermoelectric wires and 

 junctions to be embedded in them, and no wider than to admit 

 the wires and junctions (see di.igram, § 8 below). Thus, when 

 the two pieces of rock are pressed together, and when heat is 

 so applied that the flux lines are jKirallel to the faces of the two 

 parts, we had the same result, so far as thermal conduction is 

 concerned, as if we had taken a single slab of the same size .as 

 the two together, with long fine perforations to receive the elec- 

 tric junctions. The ccmipouiid slab was placed with the jier- 

 I forations horizontal, and their plane vertical. Its lower .side, 

 when thus placed, was immersed under a bath of tin, kept 

 melted by a lamp lielow it. Its upjK-r side was flooded over 

 with mercury in our later experiments (§!i 6, 7, 8), as in I lopkins' 

 experiments im the thermal conductivity of rock. Ileal w.as 

 carried off from the mercury liy a meiLsured quantity of cold 

 water (xiured ii|Kin it once a minute, allowed to remain till the 

 end of a minute, and then drawn off and immediately replaced 



1 A p.i(x:r by Ixird Kelvin, P.R.S., and J. R. Erskinc Murr.iy, rciil at 

 ihc Royal Socicly on May 30. 



NO. 1338, VOL. 52] 



