Sept. 7, 1888.J 



SCIENTIFIC NEWS. 



233 



'hat which is by no means a small thing (for it is no less than the 

 rotation of the earth), which in long-distance firing may demand 

 attention, and that to an extent little suspected by the civilian. 



Place the gun north and south, say in the latitude of London, and 

 fire a 12-mile round such as I have mentioned, and it will be found 

 that, assuming the shot were passing through a vacuum, a lateral 

 allowance of more than 200 feet must be made to compensate for 

 the different velocity of the circumference of the earth at 12 miles 

 north or south of the place where the gun was fired, as compared 

 with the velocity of the circumference of the earth at that place 

 itself — the time of flight being, in round numbers, one minute. 



At the risk of exciting a smile, I am about to assert that engineer- 

 ing has even its poetical side. I will ask you to consider with me 

 whether there may not be true poetry in the feelings of the engineer 

 who solves a problem such as this : Consider this rock, never visible 

 above the surface of the tide, but making its presence known by the 

 waves which rise around it : it has been the cause of destruction to 

 many a noble vessel which had completed, in safety, its thousands of 

 leagues of journey, and was, within afew score milesof port ; then dashed 

 to pieces upon it. Here is this rock. On it build a lighthouse. Lay 

 your foundations through the water, in the midst of the turmoil of the 

 sea ; make your preparations ; appear to be attaining success, and 

 find the elements are against you and that the whole of your pre- 

 liminary works are ruined or destroyed in one night ; but again 

 commence, and then go on and go on until at last you conquer ; your 

 works rise above ordinary tide-level ; then upon these sure founda- 

 tions, obtained, it may be, after years of toil, erect a fair shaft, 

 graceful as a palm and sturdy as an oak ; surmount it with a 

 light, itself the produce of the highest application of science ; 

 direct that light by the built-up lens, again involving the 

 highest application of science; apply mechanism, so arranged 

 that the lighthouse shall from minute to minute reveal to the 

 anxious mariner its exact name and its position on the coast. 

 When you have done all this, will you not be entitled to say to 

 yourself, " It is I who have for ever rendered innocuous this rock 

 which has been hitherto a dread source of peril " ! Is there no 

 feeling, do you think, of a poetical nature excited in the breast of the 

 engineer who has successfully grappled with a problem such as this ? 

 Another instance : The mouth of a broad river, or, more properly 

 speaking, the inlet of the sea, has to be crossed at such a level as 

 not to impede the passage of the largest ships. Except in one or 

 two places the depth is profound, so that multiple foundations for 

 supporting a bridge become commercially impossible, and the solu- 

 tion of the problem must be found by making, high in the air, a 

 flight of span previously deemed unattainable. Is there no poetry 

 here ? Again, although the results do not strike the eye in the same 

 manner, is there nothing of poetry in the work, that has to be 

 thought out and achieved, when a wide river or an ocean-channel has 

 to be crossed by a subterranean passage ? Works of great magni- 

 tude of this character have been performed with success, and to the 

 benefit of those for whose use they were intended. One of the 

 greatest and most noble of such works, encouraged, in years gone by 

 by the Governments of our own country and of France, has lately 

 fallen into disfavour with an unreasoning public, who have not taken 

 the pains to ascertain the true state of the case. 



Surely it will be agreed that the promotion of ready intercourse 

 and communication between nations constitutes the very best, and 

 most satisfactory guarantee for the preservation of peace ; when 

 the peoples of two countries come to know each other intimately, 

 and when they, therefore, enter into closer business relations, they 

 are less liable to be led away by panic or by anger, and they hesitate 

 to go to war the one with the other. It is in the interests of both 

 that questions of diff rence which may arise between them should 

 be amicably settled, and having an intimate knowledge of each 

 other, thty are less liable to misunderstand, and the mode of deter- 

 mination of their differences is more readily arranged. Remember, 

 the means of ready intercourse and of communication, and the 

 means of easy travel, are all due to the application of science by the 

 engineer. Is not, therefore, his profession a beneficeut one? 



Further, do you not think poetical feeling will be excited in the 

 breast of that engineer who will in the near future solve the pro- 

 blem (and it certainly will be solved when a sufficiently light motor 

 is obtained) of travelling in the air— whether this solution be 

 effected by enabling the self-suspended balloon to be propelled and 

 directed, or perhaps, better still, by enabling not only the propul- 

 sion to be effected and the direction to be controlled, but by 

 enabling the suspension in the air itself to be attained by mechanical 

 means ? 



Take other functions of the civil engineer, functions which, after 

 all, are cf the most important character, for they contribute directly 

 to the prevention of disease, and thereby not only prolong life, but 

 do that which is probably more important, afford to the population 

 a healthier life while livecl. 



In one town, about which I have full means of knowing, the 

 report has just been made that in the year following the completion 

 of a comprehensive system of sewerage, the deaths from zymotic 

 diseases had fallen from a total of 740 per annum to a total of 372, 

 practically one-half. Has the engineer no inward satisfaction 

 who knows such results as these have accrued from his work ? 



Again, consider the magnitude and completeness of the water- 

 supply of a large town, especially a town that has to depend 

 upon the storing-up of rain-water : the prevision which takes into 

 account, not merely the variation of the different seasons of the 

 year, but the variation of one year from another ; that, having col- 

 lated all the stored-up information, determines what must be the 

 magnitude of the reservoirs to allow for at least three consecutive 

 dry years, such as may happen ; and that finds the sites where 

 these huge reservoirs may be safely built. 



All these, and many other illustrations which I could put before 

 you if time allowed, appear to me to afford conclusive evidence 

 that, whether it be in the erection of the lighthouse on the lonely 

 rock at sea ; whether it be in the crossing of rivers, or seas, or arms 

 of seas by bridges or by tunnels; whether it be the cleansing of 

 our towns from that which is foul ; whether it be the supply of pure 

 water to every dwelling, or the distribution of light or of motive 

 power ; whether it be in the production of the mighty ocean 

 steamer, or in the spanning of valleys, the piercing of mountains, 

 and affording the firm, secure road for the express train ; or whether 

 it be the encircling of the world with telegraphs — the work of the 

 Civil Engineer is not of the earth, earthy, is not mechanical to the 

 exclusion of science, is not unintellectual ; but is of a most beneficent 

 nature, is consistent with true poetical feeling, and is worthy of the 

 highest order of intellect. 



ABSTRACT OF THE ADDRESS TO THE MATHE- 

 MATICAL AND PHYSICAL SECTION OF THE 

 BRITISH ASSOCIATION, 



By Professor G. F. Fitzgerald, M.A., F.R.S , President 

 of the Section. 



In a presidential address on the borderlands of the known delivered 

 from this chair, the great Clerk Maxwell spoke of as an undecided 

 question whether electro-magnetic phenomena are due to a direct 

 action at a distance or are due to the action of an intervening medium. 

 The year 188S will be ever memorable as the year in which this 

 great question has been experimentally decided by Hertz in Germany 

 and, I hope, by others in England. It has been decided in favour 

 of the hypothesis that these actions take place by means of an inter- 

 vening medium. Although there is nothing new about the question, 

 and although most workers at it have long been practically satisfied 

 that electro-magnetic actions are due to an intervening medium, I 

 have thought it worth while to try and explain to others who may 

 not have considered the problem what the problem is and how it 

 has been solved. 



An illustrative example may make the question itself clearer, and 

 so lead you to understand the answer better. In colloquial language 

 we may say that balloons, hot air, etc., rise because they are light. 

 In old times this was stated more explicitly, and therefore much 

 more clearly. It was said that they possessed a quality called 

 "levity." "Levity" was opposed to "heaviness." Heaviness 

 made things tend downwards, levity made things tend upwards. 

 It was a sort of action at a distance. At least it would have re- 

 quired such a hypothesis if it had survived until it was known that 

 heaviness was due to the action of the earth. I expect levity would 

 have been attributed to the direct action of heaven. It was com- 

 paratively recently in the history of mankind that the lising of hot 

 air, flames, etc., was attributed to the air. Everybody knew that 

 there was air, but it was not supposed that the upward mo:ion of 

 flames was due to it. We now know that this and the rising of 

 balloons are due to the difference of pressure at different levels ia 

 the air. In a similar way we have long known that there is an 

 ether, an all-pervading medium, occupying all known space. Its 

 existence is a necessary consequence of ths undulatory theory of 

 light. People who think a little but not much sometimes ask me, 

 "Why do you believe in the ether? What's the good of it?" 

 I ask them, " What becomes of light for the eight minutes after it 

 has left the sun and before it reaches the earth ? " When they con- 

 sider that they observe how necessary the ether is. If light took no 

 time to come from the sun there would be no need of the ether. 

 That it is a vibratory phenomenon, that it is affected by matter it 

 acts through — these could be explained by action at a distance very 

 well. The phenomena of interference would, however, require such 

 complicated and curious laws of action at a distance as practically 

 to put such a hypothesis out of court or else be purely mathematical 

 expressions for wave propagation. In fact, anything except propa- 



