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NATURE 



{Sept. 20, 1888 



The massifs of crystalline schists represented in this zone are 

 large remnants which have remained standing in ruins, the other 

 parts of the primitive rocks having subsided either en masse, 

 following great faults, or in detail, by a series of small slides, 

 following the numerous joints, or the divisional planes of 

 bedding. Not one of them represents a regular and complete 

 anticlinal fold. 



The various types of crystalline schist comprised in the Mont- 

 Blanc zone succeeded one another in the same order as in the 

 Monte-Rosa zone. They are also divided into two groups : the 

 upper group — sericitic, chloritic, and hornblendic schists ; and 

 the lower group — mica-schists and true gneisses. 



In the lower group there is a tendency towards the granitoid 

 structure, and the rocks appear more or less massive, but yet in 

 the main stratiform. They become rich in white mica, and 

 assume a granulitic texture. These phenomena are developed 

 along the anticlinal axes. 



The crystalline schists of the upper group have a tendency to 

 become richer in felspar the nearer one approaches the intra- 

 Alpine limit of the zone. It seems that this corresponds with the 

 direction in which alkaline emissions, accompanying the formation 

 of these rocks, took place, the same direction afterwards becoming 

 that of the great limiting fault of the zone. The schists -pass 

 thus into chloritic gneisses similar to those occurring near the 

 station at Modane {third zone), or to the gneiss of Arolla {fourth 

 zone) ; sometimes also into granitoid gneisses, both chloritic and 

 hornblendic, as, for instance, at Cevins, in Tarantaise. 



The tenacity of the chloritic and hornblendic schists, which 

 is generally much superior to that of the mica-schists and true 

 gneisses, and their tendency to develop felspar, which gives theui 

 greater consistency, explain the important role played by these 

 rocks in the constitution of the culminating ridges and steeper 

 massifs of the first zone. In the Mont-Blanc massif and in the 

 eastern portion of the Pelvoux massif these "needles" and 

 abruptly culminating ridges characterize the type of rock known j 

 as protogine. This name, the etymological sense of which must be 

 forgotten, has been created to designate the type of rocks which 

 predominates in the principal ridge of Mont-Blanc. The special 

 character of these rocks consists in the mica being penetrated and 

 partly replaced by chlorite. The granitoid protogine always 

 contains two felspars — orthoclase and oligoclase, part of the 

 orthoclase being usually replaced by microcline. 



Prof. Lory thinks the protogine belongs to the upper group — 

 that of the chloritic schists. In that case Mont-Blanc cannot be 

 regarded as a central arch of elevation, and its "fan-structure" 

 becomes simply a very sharp synclinal fold of the crystalline 

 schists of the upper group, isolated by two faults, along which 

 they have subsided, while acquiring a U-shaped fold. 



In the Velv oux-massif the protogine is even more largely 

 developed than at Mont-Blanc. Here also it is stratiform, and 

 alternates with chloritic gneisses like those of the western parts 

 of the massif A series of anticlinal and synclinal folds, can be 

 made out. The anticlines correspond to the Vallon des Etages, 

 the Barre des Escrins (west slope), and the Combe d'Alefroide ; 

 and the synclines to the Combe de la Pilatte, the eastern slope of 

 the Escrins (Glacier Noir), and the summits of Mont-Pelvoux. 



From observations made near Bourg-d'Oisans, the author 

 arrives at the conclusion that the protogine has originated by a 

 modification of the chloritic schists. During their formation, a 

 considerable increase in their felspathic constituent was produced 

 by granulitic emissions which took place through the gneiss and 

 mica-schists. 



Like other important features in the structure of the Eastern 

 Alps this replacement of chloritic schists by protogine follows 

 the intra-Alpine limit of the Mont-Blanc zone, which limit is 

 marked by the great fault-line which can be traced over 60 lieues, 

 from Vallonise to Airolo. This must have been the direction in 

 which took place those granulitic emissions, which, without 

 giving birth to true eruptive masses, have modified the character 

 of the old gneiss and mica-schists and developed in the chloritic 

 and hornblendic schists the felspathic character which dis- 

 tinguishes the granitoid rock known as protogine. 



THE ELECTRIC TRANSMISSION OF PO WER. 1 



"YyHAT is power, and why should we wish to transmit it? 



Power has one very definite meaning in science, and 



several rather vague meanings in practice. We speak of a 



1 Lecture delivered by Prof. Ayrton, F.R.S., at the Diill Hall, Bath, on 

 Friday, September 7, 1888. 



powerful athlete, the power of the law ; we sing of the power 

 of love ; we say knowledge is power, and so on, using the word 

 in several different senses. Now, in spite of the fact that a 

 general audience feels a little anxious as to what troubles may 

 be in store for it when a lecturer begins by being painfully exact, 

 my telling you that by power an engineer understands the rate 

 of doing work will not, I hope, make you fear that my remarks 

 will bristle with technicalities. 



When you walk upstairs you exert power — only, perhaps, the 

 one-twentieth of a horse when you go up slowly, talking to other 

 people. But when you run upstairs because you have forgotten 

 something that you intended to bring down, then your exertions 

 represent, perhaps, the one-tenth of a horse-power. You only 

 get to the top of the stairs in either case, but the breathless 

 sensation of running fast upstairs tells you that the more quickly 

 you go the harder you are working. A person exercises power 

 in the engineer's sense when he exerts himself physically, and 

 the greater the exertion the greater the power. The exercise of 

 power by the ruling classes, however, is unfortunately not 

 necessarily accompanied by any exertion, physical or mental. 



Probably the most familiar example of exerting power at a 

 distance — that is, of transmitting power — is pulling a handle 

 and ringing a bell in another room. I pull the handle, exerting 

 myself slightly, and as the result the bell at the other end of the 

 platform rings. Were not this such a very familiar operation I 

 would call it experiment No. I. You have doubtless all of you 

 performed this experiment several times to-day, and — what is all 

 important with an experiment — performed it successfully. 



And yet it was not until just one hundred years ago that it 

 dawned on people that if one person, A, wanted to attract the 

 attention of another person, B, the place where the bell ought 

 to sound was where B was, and not where A was. Indeed, in 

 many English villages down to the present day the knocker 

 principle of attracting attention is alone resorted to, with the 

 result which you may remember happened when Mr. Pickwick 

 was staying in Bath at lodgings in the Royal Crescent, and Mr. 

 Dowler undertook to sit up for Mrs. Dowler, but " made up his 

 mind that he would throw himself on the bed in the back room 

 and think — not sleep, of course. . . . Just as the clock struck 

 three there was blown into the crescent a sedan-chair with Mrs. 

 Dowler inside, borne by one short fat chairman and one long 

 thin one. . . . They gave a good round double knock at the 

 street door. . . . 'Knock again, if you please,' said Mrs. 

 Dowler, from the chair. 'Knock two or three times, if you 

 please.' The short man stood on the step and gave four or five 

 most startling double knocks of eight or ten knocks a-piece, 

 while the long man went into the road and looked up at the 

 windows for a light. Nobody came — it was as silent and as 

 dark as ever." But the tall thin man, you may remember, 

 "kept on perpetually knocking double knocks of two loud 

 knocks each, like an insane postman," till Mr. Winkle, waking 

 up from a dream "that he was at a club where the chairman 

 was obliged to hammer the table a good deal to preserve 

 order," met with the catastrophe which the readers of " Pickwick " 

 will remember. 



This episode shows what comes of having plenty of power and 

 no means of transmitting it. 



tut if some houses can still dispense with mechanical or other 

 methods of transmitting power, even to ring bells, factories cannot. 

 The looms, the lathes, or whatever the machinery used in the 

 factory may be, must either be worked by hand or foot in the 

 old style, or it must be connected with the steam-, gas-, or water- 

 engine in the new. On entering a large factory you see lines of 

 rapidly-rotating shafting, and a net-work of rapidly- revolving 

 belting, all employed in transmitting power. As a contrast to 

 this, I now throw on the screen a photograph of Sir David 

 Salomon's workshop at Tunbridge Wells, in which every 

 machine is worked by a separate electric motor, thus saving to a 

 great extent the loss of power that usually accompanies the 

 mechanical transmission. 



In America there are 6000 electromotors working machinery; 

 in Great Britain hardly 100. 



But it is not only in transmitting the power from the steam-, 

 gas-, or water-engine of a factory to the various machines 

 working in it, that electricity can be utilized. An incredible 

 amount of power is daily running to waste in this and other 

 countries because many of the rapid streams of water are too far 

 away from towns for their power to have been hitherto utilized. 



The holiday tourist, when admiring the splashing water 

 dashing over the stones, hardly realizes that the money loss is as 

 if the foam were composed of flakes of silver. 



