March 29, 1894] 



NA TURE 



507 



The curious cyclic shape of theisothermalsisdiagram- 

 matically indicated in the figure, which also brings out 

 another difference in the processes of fusion and solidifi- 

 cation. For when the liquid begins to solidify there is a 

 sharp angle in the curve, solidification being an abrupt 

 phenomenon. When the solid melts, however, there 

 is no such sharp angle, the inclined portion of the 

 isothermal gradually curves round and merges into the 

 horizontal portion which represents the condition of the 

 substance when fusion has actually set in. By repeated 

 tests the author satisfied himself that this curvature of 

 the isothermal was not the result of imperfect experiment, 

 but indicated a real condition of the substance, and it 

 may therefore be taken to correspond to a portion of the 

 continuous curve originally proposed by Prof. James 

 Thomson to express what actually goes on during iso- 

 thermal change of state, and which is predicted for 

 liquids and gases by the equations of van der Waals and 

 of Ramsay and Young. From a general survey of the 

 isothermals obtained, it appears that the volume at which 

 solidification begins, decreases, and the volume at which 

 it ends remains constant, or perhaps slightly increases as 

 temperature rises. These facts are indicated by the 



SOLID 



LIQUID 



V 



General shape of a Liquid-solid Isothermal. 



•dotted lines in the figure. We are thus enabled to map 

 •out a diagram for solid-liquid in precisely the same way 

 as for liquid-gas, and arrive at the conclusion that at 

 sufficiently high temperatures and pressures we shall 

 reach the solid-liquid critical point. As far as the present 

 -experiments go, this point lies in the region of pressures 

 above 4000 atm. and of temperatures higher than 200'. 

 When the critical point is reached, the observations also 

 show that the cyclic character of the isothermals will 

 disappear. There will be no " volume lag " during 

 vfusion. 



This " volume lag" the author regards as but a special 

 •case of hysteresis, having, besides its electrical and 

 ■magnetic analogues, its counterpart in the phenomena of 

 supersaturation, and the occurrence of all such pheno- 

 "mena he attributes to changes of molecular state. That a 

 ■similar change lies at the root of the phenomena of solid- 

 viscosity is the aim of a special series of investigations 

 ■by Mr. Barus, which are collected in No. 94 of the 

 Bulletin. The results obtained, however, are beyond the 

 scope of the present article. 



The main importance attaching to this work on naph- 

 thalene lies in the fact that it constitutes the beginning 

 of a systematic study of the phenomena of solidification, 

 which in conjunction with what is known regarding 

 liquefaction, will ultimately permit of the entire transition 

 ifrom gas to liquid and from liquid to solid being repre- 



VO. I 2/4, VOL. 49J 



sented on a single diagram. When this has been 

 accomplished, material will be to hand for framing a 

 comprehensive theory of what goes on during the obscure 

 processes of change of state. Enough has already been 

 done to give some idea of the extent to which the com- 

 plexity of an equation like that of van der Waals, which 

 mvolves but the third power of the volume, must be 

 increased when attempting to express the complete 

 passage from gas to liquid and from liquid to solid. 



J. W. Rodger, 



NOTES. 



It is announced that an International Electrical Exposition 

 will be held in Paris from July x to October 31, 1895. 



Dr. W. Havelburg has been appointed director of a 

 laboratory recently established at Rio de Janeiro for the study 

 of leprosy. 



The death is announced of Dr. L. Calderon, Professor of 

 Chemistry in Madrid University, and of Dr. Karl Schmidt, 

 Professor of Chemistry in Dorpat University. 



With reference to the brief notice of the death of Mr. W. 

 Pengelly, F.R. S., in our last number, Mrs. Pengelly points 

 out to us that "he was spoken of as Secretary, instead of 

 Honorary Secretary, of the Torquay Natural History Society, 

 a title of which he was naturally and reasonably jealous, seeing 

 that his connection with the Society was always of a donative, 

 and never of a receptive, character." 



Mr. F. Mockler's collection of relics of Dr. Jenner, 

 recently exhibited at Bristol, is now on view at the First 

 Avenue Plotel, Holborn. Admission to the exhibition is free 

 to all members of the medical profession. A movement is on 

 foot to purchase the relics as a whole by public subscription, 

 and to offer them to the Royal College of Surgeons. 



Sir Philip Cunliffe-Owen, whose death occurred on 

 Friday last, at the age of sixty-six, played an important part in 

 the development of the Department of Science and Art. In 

 1857 he was appointed Deputy-General Superintendent of the 

 South Kensington Museum, and three years later he became 

 Assistant Director. He succeeded Sir Henry Cole as Director 

 of the Museum in 1873, and held that position until last year, 

 when he retired. He did much to organise the collections at 

 South Kensington, and in the Bethnal-green INIuseum, of which 

 he was also a Director. His ability to organise, and great 

 energy, led to his appointment as executive commissioner on a 

 number of exhibitions of the works of science and the arts, and 

 for these labours, numerous British and foreign orders were 

 conferred upon him. Though not a man of science, he claims 

 our esteem for the many things he did to advance scientific 

 interests. 



The British Museum has recently acquired a section of a 

 trunk of Sequoia gigantea from California, having a diameter of 

 somewhat over 15 feet. The annual rings have been carefully 

 \ counted by Mr. Carruthers, and, two years ago, when the tree 

 I was cut down, it was 1330 years old. It was then still living 

 I and vigorous. It had, therefore, already attained a considerable 

 age when St. Augustine introduced Christianity into Great 

 Britain. The rings indicate a remarkably symmetrical growth 

 on all sides of the tree. For the first five or six centuries they 

 show a considerable annual increase in the girth of the trunk, 

 getting gradually thinner as the superficies to be covered became 

 larger, and becoming very thin for the last three or four cen- 

 turies. It is satisfactory to learn, on the authority of Mr. Car- 

 ruthers, that there were, in 1884, in all the groves which he 

 visited, trees of various ages, so that the Sequoia is in no 

 danger of early extinction. 



