372 



NA TURE 



{^August 30, 1877 



brought near them, and that they ceaseJ moving, .ind clung 

 for some time to the warmer side of a cavity. The con- 

 clusion arrived at for these phenomena is as follows :— It 

 is impossible to imagine a body which is not gaining or 

 losing heat, or at the same time gaining and losing lieat ; it 

 is therefore impossible to imagine it as entirely through- 

 out of a uniform temperature. It is evident, then, that an 

 easily movable particle, which can be set in motion by exceed- 

 ingly slight differences in temperature, will make the transference 

 of heat from one point to another plainly visible. The minute 

 bubbles in the cavities are such particles, and these vibratory 

 motions afford ocular demonstration of tne continual passage of 

 heat through solid substances. A further continuation of 

 the research was extended to the conditions under which solid 

 particles exhibit the Brownian movement. 



Concerning the presence of liquid caibonic acid in minerals, 

 Mr. Hartley finds that it is not of comraon occurrence, but only 

 occasionally met with. He also describes in his report Ihe means 

 of demonstrating in certain cavities the continuity of the g.aseous 

 and liquid states of matter as shown by Dr. Andrews in his well- 

 known experiments. Regarding the proportion of gaseous and 

 liquid carbonic acid to water in the cavities, some important 

 generalisations have been arrived at. 



Mr. Hartley gives reasons in the report which cause him to fix 

 the temperature of formation of the mineral in the case of topaz 

 somewhere above 342" C, the critical pomt of water. In certain 

 other cases in which the cavities differ in the nature of their 

 contents, the water, he thinks, must at the time of their forma- 

 tion have been in the liquid state. It is possible to determine 

 within certain limits the temperature which a rock < r mineral 

 has endured if liquefied carbonic acid is found inclosed in it. 



Rtpott on some Double Compounds of AHckel and Cobalt, by J. 

 M. Thomson. — On attempting to prepare the so-called conju- 

 gated sulphate of nickel, cobalt, and potassium mentioned by 

 Vohl (Ann. Chcm. Pharm, Ixv.), who assigns to it the formula 

 NiCoKj(S04)4 . i2H.jO, it was found that the several fiactions 

 deposited consecutively foim a sohition containing molecular 

 quantities of the simple potassio-sulphates of the two metals, 

 possessed different colours, and showed also the property of 

 dichroism to a remarkable degree. The operation having been 

 repeated several times with a like result, it was determined to 

 examine whether any regular replacement of the two isomor- 

 phous metals took place. Quantuies of the two salts were dis- 

 solved in a sufficient quantity of water, and the resulting solution 

 evaporated gently over a water bath at a temperature of So", the 

 crystals being allowed to deposit in successive fractions. 



The ci7Stals of the conjugated salts are oblique prisms, having 

 a tendency to modification when allowed to grow to any great 

 size. The first fractions have a greeriah grey colour when seen 

 in the mass, showing the preponderance in them of the nickel 

 potassic sulphate over the corresponding cobalt salt ; the latter 

 fractions, however, gradually become more crimson in colour as 

 the cobalt potassic sulphate preponderates over the nickel salt. 

 Details cf analyses are given in the report, showing the different 

 quantities of nickel and cobalt contained in the several fractions. 

 It is shown that Vohl's Ibrmula may be correct for isomor- 

 phous metals having a considerable difference in their atomic 

 weights, but fails when two metals, such as nickel and cobalt, 

 having the same atomic weights, occur in the conjugated salts, as 

 they give rise to replacements requiring a very high molecular 

 formula to express their constitution. 



The examination of the optical propeities of the several frac- 

 tions possesses some interest. It was observed that the colours 

 shown through the different axes passed in a direct order down 

 the spectrum. In the first fractions the more highly refractive 

 rays of the cobalt spectrum mingle wiih the green of the nickel, 

 whilst in the latter, the two lajs aie those adjacent to each other 

 in the cobalt spectrum. 



That these salts or fractions are not merely isomorphous mixtures 

 is shown by the fact that large crystals taken for analysis exhibit 

 throughout llie same dichroism. If, then, the phenomenon of 

 dichroism is dependent on molecular constitution, as seems pro- 

 bable, it follows that all bodies exhibiting dichroism must be 

 definite chemical compounds, and therefore the molecular for- 

 mula of some of these must be far more complicated in their 

 structure than is at present imagined. 



Abstract of the Thirteenth Report of tlie Committee for exploring 

 Kent's Cavern, Devonshire. — The Committee, in their TweUlli 

 Report, read at Glasgow last year, brouglit up the history 

 of their researches to the end of August, 1S76. They have 



now the pleasure of continuing that history to the end 

 of July, 1S77. During the intervening eleven months the 

 work has been continued without interruption, on the 

 same method and under the same daily superintendence as 

 heretofore. The workmen named in the Twelfth Report are 

 still employed on the exploration, and continue to give unqualified 

 satisfaction. 



On November 2, 1876, Mr. Busk, a member of the Com- 

 mittee, visited the cavern, accompanied by one of the superin- 

 tendents, when he inspected that portion of the work which was 

 then in progress, as well as the principal parts where the 

 exploration has been completed. 



The researches continue to attract large numbers of visitors, . 

 most of whom are admitted by the authorised guide, who, under 

 well-defined and strictly-observed regulations, conducts them 

 through such branches of the cavern as are of general and 

 popular inteiest, but not to those in which the work is in actual 

 progress:, or lias not been begun. The superintendents have 

 also had the pleasure of accompanying a large number of visitors, 

 including men of all professions and of various countries. 



The Tear's Den. — The chamber termed the Bear's Den 

 measures about sixty-seven feet in length, from north to south 

 nearly, from eight to thirty-eight feet in width, and from eight 

 to fifteen feet in height, the last dimension being measured from 

 the bottom of the excavation. The limestone roof is extremely 

 rugged, fretted, at:d water-worn. 



Adjacent to its western wall is a vast boss of stalagmite, which 

 the superintendents have preserved intact on account of the in- 

 scriptions which crowd it. One of these, " William Petre, 1571," 

 is of considerable interest on two accounts ; i, the elate is, so far 

 as is at present known, the earliest in the cavern, and the only 

 one belonging to the sixteenth century ; 2. Its genuineness can 

 scarcely be doubted, as it is known that at the period in question 

 there was a William Petre, a native of South Devon, quite a 

 young man, and a nephew of Thomas Ridgway, who. then 

 resided on the estate in which the cavern is situate, and of which 

 he was the proprietor. Moreover, in a lately discovered lease, 

 dated 1659, and conveying "closes, ffields, or pieces of ground," 

 mention is made of " one close called Kent's Hole," thus showing 

 that the cavern was so well known about the niidelle of the 

 seventeenth century as to render it probable that it was known 

 also, at least, as early as towards the close of the sixteenth. 



As the Rev. Mr. Macluiery broke ground in every p?rt of the 

 Bear's Den fifty years ago, its original condition can only be 

 learned from the description of it wtiich he has left, and which 

 may be given in the following very condensed form : — 



"The floor of the Bear's Den was studded with conical 

 mounds of stalagmite supporting corresponding pendants from 

 the roof. Fallen masses of limestone were strewed about, and 

 some of them were incorporated in the crust. An irregular 

 sheet of stalagmite, about a foot thick, overspread the floor, and 

 was based on a shallow bed of indurated rubble containing lubes 

 of stalactite collected in he.aps in parlicclir places, a great abun- 

 dance of alburn grtreum, an unusual proportion e.f bear's 

 teeth, and an iron blade much corroded. Points of sla'agraitic 

 cones were observed to protrude upwards into the rubbly bed, 

 and were found to rise from a lower sheet of stalagmite. The 

 cones of this lower sheet were precisely under those of the upper, 

 denoting that they were successively depusited from the same 

 tubes above, but the lowermost set exceeded by doable the 

 thickness of the uppermost, and the depth of the stalagmite 

 sheet was in the same proportion. The lower sheet extended 

 over the entire area of the den, but the superincumbent bed of 

 rubble, and its overlying thin sheet of stalagmite, ' thinned out ' 

 towards the sides. The removal of these partial beds displayed 

 the entire surface of the lower sheet, which exhibited a most 

 singular appearance. Over the whole area it was cracked into 

 large slabs, resembling flags in a pavement. The upper sheet 

 was not in the least fractured. The average thickness of the 

 cracked sheet was about two feet. It possessed the hardness of 

 rock, and but for its division into insulated flags it would have 

 been almost impossible to pierce it. 



" The first flag we turned over displayed a curious spectacle. 

 Skulls and bones of bear, crowded together, adhered to its under 

 surface. Flag after flag disclosed the same phenomenon ; but 

 in one place numerous skeletons lay heaped on each other ; the 

 entire vertebral column and its various other bones, even to the 

 phalanges and claws, were discovered lying in their natural rela- 

 tion, in a state of preservation .-.s if belonging to the same indi- 

 vidual. The remains of bear prevailed here to the exclusion oi 

 all other animals. Some of the teeth were of the most dazzling 



