46 REPORT — 1870, 



gas in certain specimens of meteoric iron, -whilst eartli-manufactured iron contains 

 not hydrogen but absorbed carbonic oxide gas — proving that the meteorite had 

 probably been thrown out from an atmosphere of incandescent hydrogen existing 

 under very considerable pressure, and therefore coulirming in a remarkable degree 

 the conclusions to which spectrum analysis had previously led us. The position 

 in the ranks of British science left by Graham's death will not be easily filled 

 up : he accomplished, to a certain extent, for dynamical chemistry what Dalton 

 did for statical chemistry ; and it is upon his experimental researches in molecular 

 chemistry that Graham's permanent fame as one of England's greatest chemists 

 will rest. 



As closely connected with the above' subjects, I have next to mention a most 

 important research by Dr. Andrews, of Belfast, which, marking an era in the 

 history of gases, shows us how our oldest and most cherished notions must give 

 way before the touchstone of experiment. No opinion would appear to have been 

 more firmly established than that of the existence of three separate states or condi- 

 tion of matter, viz. the solid, the liquid, and the gaseous. A body capable of 

 existing in two or more of these states was thought to pass suddenly from one to 

 the other by absorption or emission of heat, or bj- alterations of the superincum- 

 bent pressure. Dr. Andrews has shown us how false are our views on this 

 fundamental property of matter ; for he has proved that a large number of, and 

 probably all, easilj' condensible gases or vapours possess a critical point of tempera- 

 ture at and above which no increase of pressure can be made to effect a change 

 into what we call the liquid state, the body remaining as a homogeneous fluid, 

 whilst below this critical temperature certain increase of pressure always effects a 

 separation into two layers of liquid and gaseous matter. Thus with carbonic acid 

 the point of critical temperature is 30°"92 C. ; and with each given substance this 

 point is a specific one, each vapour exhibiting rapid changes of volume sind flicker- 

 ing movements when the temperature or pressure was changed, but showing no 

 separation into two layers. Under these circumstances it is impossible to say that 

 the body exists either in the state of a gas or of a liquid ; it appears to be in 

 a condition intermediate between the two. Tims carbonic acid under the pressure 

 of 108 atmospheres, and at .35^ '5 C., is reduced -j^g- of the volume which it 

 occupies at one atmosphere ; it has undergone a regular and luibroken contraction, 

 and it is a uniform fluid; if we now reduce the temperature below 31° C, the 

 liquid condition is assumed without any sudden change of volume or any abrupt 

 evolution of heat. We can scarcely too highly estimate the value of these researches 

 of Dr. Andrews. 



As examples of the power which modern methods of research give of grappling 

 with questions which only a few years ago were thought to be insoluble, 1 may 

 quote the beautiful observations, now well-lmown, by which Lockyer detennined 

 the rate of motion on the sun's surface — together with those of Frankland and 

 Lockyer respecting the probable pressure acting in the different layers of the solar 

 atmosphere, and, lastly, the results obtained lay Zcillner respecting the probable 

 absolute temperature of the sun's atmosphere, as well as that of the internal 

 molten mass. These last results are so interesting and remarkable, as being arrived 

 at by the combination of recent observation with high mathematical analysis, that 

 I may perhaps be permitted shortly to state them. 



Starting from the fact of the eruptive nature of a certain class of solar pro- 

 tuberances, Zollner thinks that the extraordinary rapidity with which these red 

 flames shoot forth proA'es that the hydrogen of which they are mainly composed 

 must have burst out from under gi'eat pressure ; and if so, the hydrogen must have 

 been confined by a zone or layer of liquid from which it breaks loose. Assuming 

 the existence of svich a layer of incandescent liquid, then applying to the problem 

 the principles and methods of the mechanical theory of gases, and placing in 

 his formulne the data of pressure and rate of motion as observed by Lockyer on 

 the sun's surface, Zollner arrives at the conclusion that the diflerence of pressure 

 needed to produce an explosion capable of projecting a prominence to the height 

 of 3-0 minutes ( = 80,000 English miles) above the sun's surface (a height not 

 unfrequently noticed) is 4,070,000 atmospheres. This enormous pressure is at- 

 tained at a depth of 139 geographical miles under the sun's surface, or at that of 



