706 kepobt— 1878. 



estimate for a very large quantity of excavation to make a sufficient channel with 

 only the remainder of the fall ; so he does. 



£ 



177,778 cubic yards of rock at 3s 29,900 



60,000 „ „ clay at Is 3,000 



237,778 „ „ 32,900 



One more curious fact is the place he excavates the rock ; that mass of rock on 

 the side of the river which is 20 feet over the river. There he has to excavate hard 

 rock 20 fest deep before getting to the river surface ; he then cuts down 6 feet 

 deep in the river : he cuts 26 feet of hard rock to get 6 feet of new waterway to 

 carry off 6 feet of water. Six feet excavated from the bed of the river will in- 

 crease the waterway to carry off as much water. as 26 feet excavation on the high 

 side, and it may be done for less cost per foot, because the bed on the other side is 

 not rock. Below the weir it is dry in dry summers, and may be easily made dry 

 in any summer. Above the weir may be dredged. Is this good river engineering ? 

 It is an example of his principle all the way up the Shannon. His proposed weirs 

 at Killaloe, Meelick, Athlone, Tarmon, Roosky, Jamestown, each occupy during 

 floods 2 feet or 2 feet 2 inches of fall, thus taking from the river surface nearly half 

 its natural fall. He has acted on mistaken principles in other points, which, added 

 to those explained, have made him estimate for three times more excavation, par- 

 ticularly in rock, than is necessary. 



The estimate -of 1867 for the whole river is £290,600. The sum which the 

 Government estimates for works in three and a half out of the seven divisions of 

 the Shannon is £300,000, which is one-half added to the estimate of 1867. At this 

 rate this revised estimate for the seven divisions would be t4?6,000. I submit for 

 consideration the following propositions : — 



1. The circumstances of the Shannon render it very easy to regulate its waters 

 and prevent injurious floods. 



2. The navigation and the drainage of the Shannon district may be improved 

 to the full extent necessary or desired for a third part of the sum which the 

 Government has been advised to insist on as necessary. This may be effected by 

 means of simple and safe removable regulating weirs, which may be all built in 

 one season, and by dynamite blasting and steam dredging. 



I have all the details to prove this for each division of the river. I have minute 

 accurate large scale maps, sections, and cross-sections of every strait and shoal, 

 with the regime tabulated for the present and for the proposed state of the river in 

 floods. 



5. On the Present State of Electric Lighting. By James N. Shoolbred, 



B.A., M. hist. G.E. 



Electric lighting has only attained to its present development by certain marked 

 stages of progress. 



Though the electric light was first produced at the commencement of tbe 

 century as a chemical experiment, yet its first stage of practical application did 

 not take place till towards 1849, when, on the recommendation of Professor 

 Nollet of Brussels, the large cumbrous magneto-electric machines of Holmes of 

 London, and of the Alliance Company of Paris, were constructed to produce a 

 current alternating in direction for the supply of a single light of considerable 

 intensity. Machines of this kind were erected at the South Foreland Lighthouse 

 in this country, in France at those of Cape Grisnez and of Cape La Heve, and at a 

 few other lighthouses in the North of Europe. With these exceptions, these 

 machines may now be considered as obsolete. 



The next stage of progress in electric machines was the result of the important 

 discovery in 1867, almost simultaneously by Sir Charles Wheatstone, Dr. Siemens, 

 and by Mr. S. R. Varley, of the principle of " reaction " between the currents created 

 by the rotation of one electro-magnet in front of another fixed one, whereby 





