8o 



NATURE 



[May 23. 1895 



Nos. 974 (6) and 974 (l) are Dutch editions by R. and I. 

 Ottens, of Amsterdam, of the Halley chart as modified and 

 found under Xo. S. 112(6). The base of the chart has been 

 changed, but not the lines of equal \-ariation. The dedication to 

 Prince George has been omitted. The dates a.ssigned by the 

 Catalogue are res|x;ctively I73S(?) and 1740. The chief interest 

 in these Dutch reprints lies in the fact that they have a French 

 text pasted on the left-hand side, and a Dutch text on the right- 

 hand side, over Halley's name. 



No. 974 (4). " A new and correct Chart showing the Varia- 

 tions of the Compass in the Western and Southern Oceans, as 

 observed in y* Year 1700 I)y his M.i'''* Command liy Edm. 

 Halley." Date given by the Catalogue, 1720, marked doubtful. 

 This chart extends from 59° X. to 59° S., and from 2iA° E. to 

 100° W. of London. It is enclosed by a border ; the base of 

 the chart is entirely different from that of 974 (5) ; yet the equal 

 variation lines, as far as given, are identical w ith those for the same 

 region on 974 (5). In but one respect is there a diflference in 

 the lines, viz. in no case are they drawn over the land, and in a 

 few cases, also, they are slightly extended. It contains in addi- 

 tion the course of the Paramour Pink, the ship in which Halley 

 made his obsenations, 1697-1700, with the chief aid of which 

 he drew the equal variation lines for the .Atlantic Ocean. But 

 the matter of chief importance is that this chart is dedicated to 

 King William JII. This fixes its date. William III. died 

 March 8, 1702. It is highly probable, then, that this is the 

 chart published in 1 701, referred to by Halley in the above quo- 

 tation, and. in consequence, the original HalUy chart. It is, 

 moreover, rc-asonable to suppose that Halley would dedicate 

 his first chart to King William HI., who had furnished the 

 means for the making of the observations, to which the chart 

 was due. This chart has escaped the attention of all geomag- 

 neticians and biblic^raphers, and the British Museum copy may 

 be the only one in existence.' 



.\nother matter of historical interest, ap|arently unknown to 

 all modem authors in terrestrial magnetism, wa-s ascertained. 

 I find it as.serted that the Krenchman, I,. I. Duperrey, was the 

 first (1836) to construct the " .Magnetic Meridians" for the whole 

 earth, i.e. those lines on the earth's surface marking out the path 

 (lescrilxrd by following the direction jwinled out by a compass 

 needle. It seems, however, that this honour should be accorded 

 to an Englishman, Thomas Yeates, who, in 1817, published 

 a chart of the Lines of Equal Magnetic Variation, accompanied by 

 a " New and .Accurate Delineation of the Magnetic Meridians."' 

 \ second edition of this chart was published in 1 824. Copies of 

 both editions were found in the British Museum. 



Washington, April 20. L. .\. Baiter. 



The Unit of Heat. 



Dr. Joly's strictures on the units of heat at present in use 

 will meet with a ready endorsement from those who have worked 

 on calorimelry. The large calorie is too large for convenience 

 in most cases, and the small calorie is too small, while the con- 

 fusion created by different writers using different units with the 

 same name is scarcely reduced by their writing one with a capital 

 and the other with a small <•. A unit of convenient m.Tgnitude 

 would be one equivalent to about 100 small calories, and 100 

 calories has, indeed, been adopte<l as a unit by more than one 

 writer on thermochemistry. There is, however, what may be 

 termed a natural quantity which is nearly equivalent 10 such a 

 unit, namely, the heat of fusion on r)ne ^ram i)f water at 0° C. , 

 which is nearly eighty calories. This apixrars to Ix; just as suitable 

 from other |x>inls of view as the heat of va|X)risation of one gram of 

 water at constant temiieralurc and 760 m.m. pressure ; and if this 

 latter can \k rccommeniled on the ground that in defining it we 

 replace the thermometer by the larometer, the former will |x>ssess I 

 the su[)erior claim of (for all practical purposes) not depending 1 

 even on the liarometer. t 



If I rememl)er rightly, this unit has already been adopted in one , 

 work on ihermochemisirj'. 1 



No doubi the heat of liision of water requires redetermination; i 

 but it should lie determinable with quite as much accuracy as the 

 heat of va|K>risa(ion, 



Neither of these prM|Mised units, however, jxissess what should 

 lie the chief chararleristic of a physical unit, namely, a simple 

 relation to other units; and before adopting either of Ihcm, it 



* Upon furnUhinK Prof. Hrllmann with .it>ricr rlcvrription of lhi« chart, he 



h;»v f .iKi'I tli.ii I. Mnriiif in l,i, " lx)ix du Magn^li^me," Piiri«, 1776 and 



*' '('•llmiirm'" copy of the H.-iIlcy ch.trt i» n 



-.vith ihc exception thai it cmhriicc* Init 



would be well to consider whether some convenient unit related 

 to, say, the electrical units, could not be adopted. A Committee 

 of the British .Association would be a body most suited to in- 

 vestigate this matter. 



Yax practical purposes, a quantity which is even of greater 

 importance than the ni.ignitude of the unit adopted, is the relative 

 value of the heal capacity of water at different temperatures. 

 In spite of the large amount of wurk which li.is been expended 

 on this subject, great uncertainty still prevails respecting it. The 

 heat ca]>acity of water, and the heat of fusion of ice, are subjects 

 which I have been for some years intending to turn my attention 

 to, and the work is now practically in hand. 



Harpenden, May 4. SrENCER I'lrKERiNr,. 



NO. 1334, VOL. 52] 



Mv objection to the latent heat of water unit is that this is .an 

 inaccessible unit on account of the difiicullies attending measure- 

 ments with the Bunsen calorimeter. 



.Some years ago I began experiments on a gravimetric ice 

 cilorimeter. I have not had leisure to go on with them, but the 

 results obtained were verj' encouraging. The substance wa.s 

 cooled below 0° while hanging sus|>ended from one arm of a 

 chemical lalance. This was effected in a double-walled chamber 

 of copper. .\ tube, stopped by a plug, connected this chamber 

 with a reservoir of water and clear broken ice. The water w,i.s 

 previously boiled to expel air. On raising the plug the water at 

 o' flows r.apidly into the calorimeter, and a shell of clear ice forms 

 u|ion the substance. The effect on the Ijalance is noted, and by 

 observing the change of buoyancy iiiHin the melting of the ice, 

 and knowing the density of ice at o\ the mass of the latter can 

 be estimated. The weight measurement will extend to about 

 0'5 of a calorie. In the steam calorimeter the weight measure- 

 ment extends to 01 calorie, or even less. 



There is, of course, much to be s;iid for a thermo-dynamic 

 unit. The question is certainly deserving of having the opinions 

 ami views of scientific men fully expressed ujxut it — as Mr. 

 Pickering suggests. A glance at any of the recent accurate 

 thermal work done in England will show what confusion there 

 exists as to what is the calorie, and as to how all the pet calories 

 of various physicists arc related. To render many old measure- 

 ments of value, this last question should be decided. It reminds 

 one of the state of therm<mietry in De Saussure's time. 



Trinity College, Dublin. J. J'll.V. 



Reputed Traces of Negrito Pygmies in India. 



May I be permilled to suggest to readers of M. i,)uatrefages' 

 work on the Pygmies, the l'".nglish edition of which has recently 

 been reviewed in Natirk, to pause before accepting his cim- 

 clusions as to traces of Negritos being found in peninsular 

 India. 



The evidence he relies on ]xirtly consists of a description by 

 M. KoHs,selet of a half.starved wanderer from .Sirjuga, whom 

 he assigns to the race Bander Lokn (or, as it is printed in the 

 English edition, Bandra Lokh) ami the tribe Djangal. -Any 

 .Anglo-Indian with the slightest knowledge of the language, not 

 to s;iy of ethnology, would be amused at such nicknames being 

 applied .as definite racial terms. The first simply means 

 monkey-people (equivalent to sitvage), as apjilied by dwellers 

 in the plains to the wilder inhaliitants generally ; and the 

 second, if it can be said to mean anything in the form i)resented, 

 is sim])ly *' jangli,'' or a dweller in jungle. 



The |>ortrait of this " Djangal," from a r.apid pen and ink 

 sketch, is a caricature of a somewhat exceptional and by ni> 

 means lypiial individual, and .affords no tnistworthy material 

 for an ethnological iliscussion. 



The "fever-stricken inaccessible" region .Sirjuga,' from 

 whence this S|x;ciinen was a fugitive, according to M. Rousselel, 

 is well known to me, and when I ravelling there I spent s<ime d.iys 

 in the com|)any of the late (ieneral Dalton : and not only then, 

 but in connection with the production of his great work on 

 the Ethnology of Bengal, to which I had the privilege of con- 

 tributing, I had many conversiitionswilh him regarding the tribes 

 of that region. I was, imireover, well acquainted with the true 

 Negritos of the Andainans, of whom I had then already seen many ; 

 and I do not hesitate to say that I never met with ihe slighlesl 

 trace of a Negrito element among the numerous tribes I became 

 acquainted with during many years travelling in llie hilly Iracis 

 of Western Bengal, the Central Provinces anrl ihe Northern 

 Provinces of Madras. Inilividuals lielonging loilifferent tribes 



1 The (lintricl of Sirjiig.-i in Cholo Nngpur \% nol nc.ir .\incrk.inlak, nor is 

 it included in ihe Vindhyan Kangc a* is stated hy M. QualrcfaBcs. 



