628 



NA TURE 



[October 27, 1904 



sequent report of this discussion in your Journal these views 

 were suppressed. The abstract of the rejected paper was 

 printed in the annual report of the British Association, just 

 issued, among the Section B papers, from the oflRcers of 

 which section I had received uniform courtesy and consider- 

 ation throughout the transaction. 



Now such a joint resolution as I have mentioned ought 

 to have precluded any referee from rejecting a paper which 

 had already been approved, and I have to suggest that a 

 by-law be framed to render an occurrence of this kind 

 impossible in the future. William .Ackuovp. 



Striped Haw^kmoths in Sligo. 



There has been a letter or two in recent numbers of 

 Nature on the finding of rare moths in England. It may 

 be of interest to the writers to know that in the middle 

 of last September there was caught in the town of Sligo 

 a specimen of the striped hawk-moth. It w-as captured in 

 the printing office of the SUgo Independent, its great bulk 

 lirst attracting attention and then its beautiful markings. 

 I know but very little about insects, the honey bee excepted, 

 but I carefully compared the living object with a description 

 and coloured plate in a woric on Lepidoptera, and have no 

 doubt but that it was the very thing your correspondents 

 are making so much ado about. It is now preserved in a 

 little collection of Mr. Irvine (Ratcliffe Street), but the 

 gorgeous colouring has all gone, and the striping is barelv 

 traceable. I have been told that another e.xactly similar 

 moth was found last year a few miles from Sligo along the 

 sea coast. 



I never noticed one of these insects before, but if it be 

 such a rarity in the British Isles as your correspondents 

 seem to hold, it is easy enough to account for its presence 

 in the present instance. Sligo is a sea-port town, and in 

 August last a cargo of timber from, 1 was told, South 

 Amarica was discharged. Most likely the eggs came over 

 in the timber and were here hatched out. 



Joseph Meeh.an. 



Creevelea, Drumkceran, co. Leitrim. 



is bluwn ill bv powerful high-speed fans working' with 

 a water-gauge of nearly 9 inches, the other being the 

 outlet; in case of derailment of a train occurring it 

 cannot possibly run into a train in the opposite direc- 

 tion ; when repairs are required one tunnel can be 

 closed for a time, the trafific being conducted in the 



Fig. I. -The Gn 



allons per 



other; and finally, which is most important, the 

 crushing weight of the material overhead is much 

 more easily dealt with than it would be in a 

 double line tunnel. When it is remembered that the 

 overlying rocks extend to a height of 7005 feet, and 

 that the workmen are at the enormous distance of 

 nearly lA miles below the surface, or 50 per cent, more 



THE SIMPLON TUNNEL. 

 A S the Simplon Tunnel is rapidly approaching com- 

 -^*- pletion, natural curiosity is aroused as to thi' 

 extent to which the accuracy of the alignment has bi c n 

 attained. This is a riddle which can only be answei( d 

 when the last metre of rock has been removed and tin 

 two headings unite. 



It was hoped that this international meeting ot 

 Switzerland and Italy, under Mont Leone, wouldtakt 

 place in October, but in consequence of unexpected 

 difficulties which occurred early in September, it is 

 probable that the actual junction will not occur so 

 soon. 



The setting out of the centre line of the tunnel is 

 done every month by the company and contractors, 

 but, in addition to this, the work is checked several 

 times in the year by the Government engineers. On 

 these occasions the work in the tunnel is entirely 

 suspended, so as to ensure that the atmosphere for 

 the entire length shall be bright and clear. A small 

 slit of light is thrown into the tunnel bv means of a 

 powerful lamp, and by the aid of theodolites this is 

 taken right up to the working face. It is anticipated 

 that when the actual meeting occurs the error in level 

 will be nil, and that the error in direction will be 

 under eighteen inches. 



.^s our readers know already, the length of the tunnel 

 will be I2i miles, all of which has been penetrated 

 with the exception of a short distance of about 260 

 yards near the middle. The work consists of two single 

 line tunnels 50 feet apart, axis to axis, and the object 

 of having two tunnels in place of one has been fully 

 justified by later experience, and for the following- 

 reasons. The ventilation is much more efficient, one 

 tunnel being used as an " intake " for fresh air, which 



NO. 1826, VOL. 70] 



rill at work at the " 

 of heading 10 feet 



Daily progress 18 feet. 



than man has ever been heretofore, it will be realised 

 that not only is the pressure enormous, but the heat 

 is also great; in fact, the pressure which has been 

 encountered is so great that in one place the arching, 

 consisting of granite blocks, is 2 metres in thickness. 

 The tunnel is arched throughout, as it was deemed 

 advisable that no risk should be incurred of even a 



