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NATURE 



[May 29, 1890 



A rock-mass behaves as a viscous body, under slight 

 pressures, when heat and the presence of water have over- 

 come the cohesion of its particles. But the researches 

 of Tresca and Uaubr(!e have shown that, when subjected 

 to sufficiently powerful stresses, the most perfectly solid 

 bodies we know of behave like viscous bodies, and can be 

 made X.oflow- 



In the foregoing remarks, my main object has been to 

 show how far the physical and chemical principles, which 

 have been established by actual experiment, are capable 

 of explaining the phenomena observed by the geologist 

 in studying the earth's crust. I have especially avoided 

 invoking any causes which must be regarded as hypothe- 

 tical. 



Some of the actions relied upon as explaining the origin 

 of the great features of the rock-masses which compose 

 the earth's crust may seem at first sight small and even 

 insignificant. But the great lesson taught by modern 

 geological science is that such small forces, operating 

 upon enormous masses of matter during vast periods of 

 time, are capable of effecting the most stupendous results. 

 In speaking of j/«//trt/ pressure, I have net treated it 

 as an agent of change, like heat or electricity, but simply 

 as a condition under which these agents operate — one 

 which may profoundly modify or control their action. 

 Such pressure, too, may produce great effects by causing 

 a closer contact and consequent chemical action between 

 the molecules of a fluid made to penetrate a solid, or be- 

 tween the molecules of two solids forced into more perfect 

 contact. Statical pressure may, further, prevent the 

 escape of volatile materials even under extreme tempera- 

 tures, and these substances, as in the case of the 

 " mineralizers " of the French chemists, may exercise 

 important influences on the solids or hquids within which 

 they are retained. 



Dynamical pressure, especially when it results in 

 differential movements in a mass, can certainly do all that 

 is effected by statical pressure, and perhaps something 

 more. That such motion is converted into heat there 

 •can be no doubt ; and some geologists, like the late R. 

 Mallet and Prof. Prestwich, have argued that the heat so 

 produced must have played an important part in the 

 work of metamorphism. But considering the slowness 

 with which the earth-movements have probably taken 

 place, and the opportunities for the dissipation of this 

 thermal energy, it may be regarded as at least doubtful 

 if at a particular point in the rock-mass the temperature 

 could ever have been raised to such an extent, that any 

 very important part of the work of metamorphism ought 

 to be ascribed to it. In the same way, we may, perhaps, 

 regard the suggestion of Mr. Sorby that, during great 

 earth-movements, mechanical energy is directly converted 

 into chemical energy, as one in favour of which no con- 

 vincing evidence has as yet been adduced. 



It is at least conceivable that the realm of excessively 

 high pressures is one in which phenomena may be dis- 

 played which are as anomalous as those exhibited under 

 extremely low pressures— the high vacua of Mr. Crookes. 

 But until such effects have been demonstrated by actual 

 experiment, it is unwise to invoke their aid in geological 

 hypothesis. My great object, in the remarks I have 

 ventured to offer you this evening, has been to show that, 

 on well-established physical and chemical principles, the 

 phenomena, which are exhibited by rock-masses that have 

 been subjected to great pressures, are capable of satis- 

 factory explanation. 



THE UNIFORM PENNY POST. 



OF all the jubilees that are now being celebrated, 

 there is none which has had a more beneficial 

 influence on the age than that celebrated last week at 



NO. 1074, VOL. 42] 



the Guildhall, with such success and good management. 

 There are some who deplore the decay of letter-writing, and 

 even a few who regard the penny post as an unmitigated 

 evil, but no one can fail to perceive that the conduct of 

 the great commercial business of this country would have 

 been impossible without cheap postage. 



We are not celebrating the penny post. This was 

 proposed in 1659, by one John Hill, an attorney of York 

 —curiously enough a namesake of Sir Rowland's— who 

 showed its practicability and advocated free trade in 

 letter-carrying. He proposed a rate of id. in England, 

 2d. in Scotland, and ^d. in Ireland, as well as 3</. 

 per ounce for small parcels. 



Nor are we celebrating the invention of adhesive 

 stamps, but the introduction, in 1840, of that great 

 measure which swept away a shding scale of postage of 

 single letters written on single sheets of paper which 

 varied between 4^'. and is., and a system of franking that 

 had grown, even in the reign of our present Queen, to a 

 most shameful abuse. Envelopes or covers and enclosures 

 involved double postage. If the letter weighed an ounce 

 the rate was quadrupled. A single letter, London to 

 Brighton, cost 8</., to Edinburgh is. i^d., to Cork is. id. ; 

 or if it weighed i| ounces, to Edinburgh js. jhd., to Cork 

 ()s. lid. The number of letters passing through the post 

 in 1839 was 76,000,000. In 1889, it amounted to 

 1,600,000,000, and this excludes newspapers, post-cards, 

 books, and parcels. The grand total for 1889 was 

 2,362,000,000. 



It is not too much to say that the transport of this 

 enormous mass of material would have been impossible 

 but for the advent of steam. Railways and steam-boats 

 have led to the possibility of the uniform post. Telegraphs 

 have made its administration practical and simple. 

 Without these practical applications of science its suc- 

 cess would have been impossible. Pack-horses, mail- 

 coaches, and sailing-vessels, would have failed to transport 

 mails with the celerity, trustworthiness, and regularity, 

 that are the essentials of a true postal service. 



The Stuarts made the Post Office a monopoly of the 

 Crown ; and the Commons, who in Charles's day de- 

 nounced the establishment of the monopoly, promptly 

 proceeded by Cromwell's soldiers to put down John Hill 

 and his free trade in letters. It has remained the 

 monopoly of the State, and its work is well done, but this 

 is due to the fact that it is so well supervised by the public 

 itself, every member of which is interested in its well- 

 working. If the breakfast table is not garnished with the 

 expected letters, if any abuse, want of accommodation, or 

 delay occurs, the press or the House of Commons soon 

 wants to know the reason why, and the remedy is at once 

 applied. In fact, the public is the master and the postal 

 service knows it. In no service in the world can there be 

 found more zeal, energy, and attention. The rewards are 

 not quite so evident. Although this is the jubilee year, 

 Post Office names were conspicuousby their absence from 

 the Queen's Birthday honours, and even such ardent re 

 formers as Mr. Henniker Heaton, with an ignorance that 

 is surprising, speak in contemptuous terms of the unim- 

 pressionable mind of the red-taped official. 



The most scientific branch of the Post Office is un- 

 questionably the telegraphic. Many fears were enter- 

 tained that its efficiency would deteriorate under the sup- 

 posed chilling influence of Government monopoly, but 

 these fears have not been realized. Facilities have been 

 increased, business has been developed, improvements 

 have been introduced, new processes have not only been 

 adopted but originated, and our Postal Telegraph De- 

 partment unquestionably holds the most prominent posi- 

 tion in the world at the present moment. The number 

 of messages, which in 1869, the year before the transfer, 

 amounted to 6,000,000, now reaches over 60,000,000. 

 Duplex, quadruplex, and sexuplex methods have been 

 made practica'. The automatic system of Wheatstone, 



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