288 



NA TURE 



yjuly 24, 1884 



sea of pumice which resulted from the eruption of Krakatoa, that 

 you may perhaps not be indisposed to print it in Nature. 

 University of Edinburgh, July 17 Wll. Turner 



71, Rue de Cenl-'c, Aix-les-Bains, June 24, 1884 

 Dear Professor Turner, — I have been so occupied since 

 meeting you in Edinburgh that it has been impossible to send 

 sooner notes of my trip to Java. The first intimation that I had 

 of anything unusual having occurred was on our way out to 

 Australia. Making our way north again after having done our 

 "easting" in about 45' S., we were all much struck by the 

 splendidly vivid sunsets, and by the distinct interval of time 

 between the actual disappearance of the sun below the horizon 

 and the appearance of the deep red or crimson glow. This 

 phenomenon was more striking as we sailed north. On reaching 

 Queensland we heard of the volcanic eruption in the Sunda 

 Straits and received the explanation of the so-called "Krakatoa 

 Sunsets." I left Newcastle, N.S.W., for Batavia in a steamer 

 ali' mt November IO, iSSj, via Cape Leeuwin, sailing up the west 

 coast of Australia. We first came across distinct evidences of 

 the eruption about 200 miles before we entered the Straits of 

 Sunda, in small isolated pieces of pumice-stone, which became 

 much more numerous and finally took the form of yellow patches 

 constituted by morsels of pumice varying in size from a pea or 

 even smaller up to a cocoa-nut, rarely larger. As we neared 

 Krakatoa itself, these patches were certainly more numerous and 

 larger in size, but still the actual amount of debris was small, 

 much smaller than I had expected to find after the account I had 

 heard from persons who had previously traversed the Straits. 

 The yellow patches were few and far between, and composed 

 chiefly of a coarse dust with here and there larger lumps amongst 

 it. Krakatoa, formerly the most fertile of all the lovely isles 

 which one passes, rose like a vast cinder, still smoking. Not a 

 blade of grass or a leaf was to be seen, just a grayish seared-looking 

 mass. A large portion of the island had disappeared, and I was 

 told that over the sunken part 300-fathom soundings had been 

 taken. Between the island and Batavia we passed a few more 

 floating patches of pumice as above described. After about eight 

 days at Batavia we steamed down the coast to different ports, 

 Cheribon, Tegal, and Samarang, being on the whole about three 

 weeks away from the time we left Batavia to our return there, 

 which took place, so far as I can remember, on January 1. On 

 nearing Batavia again we passed through large patches of pumice- 

 stone, patches of several acres in extent, some of the lumps 

 forming them being of large size, roughly speaking about as big 

 as a cwt. sack of coals, and all sizes below that down to 

 coarse dust. We anchored for the night just outside the port in 

 xlear water. Early in the morning one of the officers called me 

 to look at an immense floe of pumice-stone that was bearing 

 down upon the ship, and very soon we were entirely surrounded, 

 and formed the centre of about, I should think, a square mile. 

 Though covering a large surface, there was evidently no great 

 depth of matter. One could pick it up by throwing a bucket or 

 heavy pail into the mass, and a small steam launch easily made 

 her way through it to our side. We left Batavia early in the 

 morning, and passed through two or three such collections, all 

 making their way in the same direction by the action of a current, 

 as there was no wind, the sea being perfectly calm. When 

 about thirty miles from Batavia, we met coming towards us 

 an immense field, similar, except for its greater extent, to those 

 already described. I could not tell you by any means exactly 

 how large a surface it covered, but at one time could only just 

 make out the edge we had entered it at with the naked eye, and 

 could not see its termination in the opposite direction with the 

 ship's glass, so that it was at least several miles in extent. Also 

 the depth of the pumice-stone bed was very great, offering con- 

 siderable resistance to the ship's progress, as shown by its dimi- 

 nished speed. An iron fire-bar thrown over the side rested on 

 the surface of the mass, instead of sinking. Large trunks of 

 trees were not floating in the water, but resting on the surface of 

 the pumice. The passage of our vessel left a wake of only a few 

 feet, which speedily closed in again, so that to see it at all I had 

 to lean over the stern and look under it as it were. It seemed 

 exactly as if we were steaming through dry land, the ship acting 

 as a plough, turning up on each side of her a large mound of 

 pumice, especially noticeable on looking over the bows. Our 

 passage through this made no great noise — just a soft sort of 

 crushing sound. The effect was very striking and queer. I only 

 regret that I did not time our passage through this, the largest 

 mass we met. We passed through one more but smaller field in 

 the Straits of Sunda, and after that do not remember again 



meeting witli any even small patches of pumice-stone. I thought it 

 curious meeting such immense quantities of the debris in the 

 same place where, a month or five weeks earlier, only a few 

 scanty, isolated patches existed. It was not due to a new erup- 

 tion, so must be accounted for by the currents massing together 

 a large number of scattered patches ; or perhaps a certain 

 amount had first sunk, and then, later on, had risen to the sur- 

 face. I hope these short notes may be what you want ; if I can 

 give you any more information, I shall be delighted to do so. 

 With kindest regards. 



Believe me yours sincerely, 



Stanley M. Rendall 



The Laws of Volume and Specific Heat 



The former, known as the "law of Avogadro," implies that 

 any given volume at the same temperature and pressure must 

 contain the same number of molecules. It includes the law of 

 Chasles, viz. equal expansibility for equal increments of heat ; 

 and the law of Boyle or Marriotte, that the volume of any gas 

 must vary inversely as the pressure. 



The other is that of Dulong and Pettit ; and as the former 

 necessitated equal volumes, so this latter implies constant heats 

 for parallel conditions. But, finding that few elements approxi- 

 mated this law, it was an early device to double, treble, or 

 quadruple the old atomic weights to secure a supposed uni- 

 formity ; and thus the law found this expression, viz. that the 

 specific heat of any solid element would prove to be a measure 

 of its atomic quantity. 



This, put in plausible fashion, will be the stock instruction of 

 the superficial books for some time to come ; but in the higher 

 circles of chemical life it is being admitted more and more that 

 a great change has come over the spirit of this dream. Depar- 

 tures from the normal 6 "4 are no longer attributed to errors of 

 observation, and that constant is replaced by a range of 5 "5 to 

 6 '9 ; while, to keep within this, M. Weber has proved that the 

 doubled carbon equivalent must be tested at a range of tempera- 

 ture exceeding 1000° C. He has found that within the limits of 

 - 50 and 600° its heat value increases sevenfold ! Well indeed 

 may he say, " The idea that temperature can be overlooked 

 must no longer be entertained;" also, " That the specific heats 

 are not generally expressed by constant numbers ; the physical 

 condition of the elements influence their specific heats as much 

 as their chemical nature." 



These be great admissions from one of the highest authority, 

 but they are as nothing compared with the new demands of 

 physical chemistry. Mr. J. T. Sprague, an able and deter- 

 mined new chemist, has been the first in England to challenge 

 attention to the recent researches of M. Berthelot, L. Troost, 

 and others of the very highest chemical authority. 



In a recent paper he admits that the new results " strike at 

 the root of the most favourite chemical doctrines of the day, 

 doctrines which are the foundation of the modern atomic weight 

 and molecular theory, and consequently of the doctrines of 

 atomicity, and the complicated molecular theories which have 

 been based upon the supposed atomicity and specific bonds of 

 different atoms." 



The laws of Avogadro and Dulong and Pettit are offshoots of 

 one principle, and one really implies the other, //"true, it would 

 follow that the atomic heat must be the same for all substances, or, 

 if otherwise, the same quantity of heat would not produce equal 

 expansions ; also that the specific heats must be equal at all tem- 

 peratures, or equal quantities of heat would act differently at 

 different temperatures, or else it must vary equally for all gases, 

 or they would expand unequally for equal quantities of heat. 



Now it is a misfortune for these laws that none of these condi- 

 tions subsist over wide areas. As a consequence of the two laws, 

 an air thermometer should measure all temperatures by equal 

 rates of expansion, and a given expansion should correspond to 

 a fixed quantity of heat ; such a thermometer should also read 

 equally if filled with any other perfect gas. 



In other words, these laws can only be true if the relation 

 between the weight and volume of different gases be constant, 

 and if the heat absorbed in producing a given change of volume 

 is equal at all temperatures ; that is, if the specific heat is 

 constant. 



These conditions are practically fulfilled by air, O, N, and H, 

 between 0° and 200° C, so that the scale of temperature derived 

 from the change of volume is the same as the scale derived from 

 quantities of heat ; but between 200° and 4500 there is a gradual 

 growth of changed conditions which proves fatal to both laws, 



