68 Sir J. South — Vibrations caused by Railway [1863. 



still parallel to No. 3. As the tremors became more distant, these trans- 

 formations of the image take place in a reverse order, mitil the star 

 resumes its original disk-like form. 



These results were strongly conspicuous even in a fully illuminated field, 

 and equally so whether the magnifying power was 60, 200, or 750. The 

 phenomena are very striking, from the contrast between the smaller images, 

 which are blue, while the larger ones are reddish, and from the sudden 

 way in which they break out. 



The nights of the 13th and 14th were fine, and so thoroughly confirmed 

 my previous observations that I felt it my duty to lose no time in informing 

 the late Lord Auckland, then First Lord of the Admiralty, of the preceding 

 details and of my conclusions from them, that a tunnel did not prevent 

 great tremors from being propagated from it when a train was traversing 

 it, certainly to the distance of 643 yards, and probably much further. 



The impression which these facts made on his Lordship he expressed 

 in the following letter. 



Copy of a Letter from the Earl of Auckland to Sir James South. 



"Admiralty, January 26th, 1847. 

 "Sir, — I have to return you many thanks for the very interesting 

 report which you sent to me of your experiments upon the distance to 

 which the vibration caused by steam-carriages within a tunnel extend ; 

 and I cannot but admire the enterprise and ability with which these expe- 

 riments were conducted. They would be quite conclusive if the question 

 of carrying a tunnel through Greenwich Park were again to be agitated. 



"I am, very faithfully yours, 

 *'To Sir James Souths ^c. ^-c." "Auckland.'* 



The reserve with which I spoke of that further distance arose from the 

 circumstance that I was not in possession of the exact measurements of the 

 tunnel and the position of its shafts. I had twice applied for them in vain 

 to the railway authorities, and was obliged at last to execute the measures 

 myself*. This consumed some time, and the observations were not com- 

 pletely resumed till February 24, 1847. 



The process was this. About 600 yards before the entrance of the 

 tunnel a rocket was fired as a signal for attention. At the instant that the 

 engine passed the south end of the tunnel, one of Lord Essex's game-keepers 

 fired one barrel of his gun, and the other about a second after, which was 

 necessary to distinguish this from the shots of poachers, who were often at 



* This delay was not occasioned by any want of courtesy on the part of the Directors 

 or other officers ; from whom, especially from Mr. Creed, their Secretary, I received the 

 heartiest cooperation. He not only directed all the officers along the line to aid as far 

 as possible my investigations, but pressed on me free passes for myself and my assistants. 

 I was also indebted to Captain Bruyeres for the character of the trains, and to Mr. Stubbs, 

 the Superintendent of the Watford Station, for the zeal with which he followed out the 

 Secretary's instructions at much personal inconvenience. 



