86 REPORT — 1853. 



III. The Committee next endeavoured, by circular, to obtain the coopera- 

 tion of a limited number of gentlemen, whether in the British Islands or in 

 foreign parts, who by their possession of instruments of adequate optical 

 power, habits of astronomical observation, and available leisure, might be able 

 and willing to undertake definite parts of the great task which they hoped to 

 see accomplished. 



IV. To these letters, the replies which have been received offer in general 

 very satisfactory assurances of cooperation ; and in some cases useful addi- 

 tional suggestions and notices of interesting facts are added. In particular, 

 the author of'Der Mond," besides assuring the Committee of a general de- 

 sire to cooperate in their labours, states the degree in which, since his appoint- 

 ment to the Observatory at Dorpat, he has been able to extend his former 

 observations on the " light streaks" of the moon, an object to which the Com- 

 mittee had ventured to specially direct his attention, and instances the di- 

 stinction which he has already made between the " light spots" which vanish 

 in lunar eclipses, and those which remain visible and even grow more distinct 

 in the shadow, except where it is deepest. 



The Committee do not, however, feel it to be proper now to report the 

 special views and limited progress of their members, beyond placing before 

 the Association one drawing of the Mountain Gassendi — on the scale proposed 

 for the whole survey — made from a telescope mounted at York by one of 

 their members. 



Provisional Report on Earthquake Wave-Transits ; and on Seismome- 

 trical Instruments. By R. Mallet, C.E.,M.RJ.A. {In a Letter 

 to the Assistant-General Secretary.) 



The grant of £50 made in 1850, for measurement of earthquake wave- 

 transit, has been wholly expended, in addition to a sum a good deal exceeding 

 its amount, upon the experiments on transit made at Kiiliney Bay and 

 Daikey, as reported in the last volume but one of our Transactions. Prior 

 to the conclusion of the above experiments I had made some progress in the 

 construction of a self-registering seismometer, upon principles already placed 

 before the Association. 



Within the last year other unavoidable occupations, and the work of 

 preparing and discussing the large Earthquake Catalogue, have much 

 interfered with the progress of the seismometer: I expect to be able at 

 the meeting succeeding the present to exhibit the instrument, or perhaps to 

 have had it previously set to work for a time. 



Galvano-telegraphic combinations recently brought into use, and especially 

 the beautiful arrangements for simultaneous astronomical transit observations 

 adopted by the Astronomer Royal, leave no room to doubt that any dif- 

 ficulties in applying such methods to seismometry may be fully overcome. 



The great Earthquake Catalogue, due almost wholly to the devotion and 

 labour of my eldest son, Dr. John William Mallet, has been entirely completed 

 and discussed, and the results reduced to curves. The first portion of the 

 catalogue is already printed in the last volume of our Transactions, and ail 

 the remainder is ready for press, and with the discussional results can 

 appear in the volume for 1853. 



At the meeting of the Association, September 1852, a grant of £50 was 

 made to me for the purpose of extending experiments upon earthquake 

 wave-transit, availing myself of the mining operation sin progress at the quar- 

 ries of Holyhead Harbour. With a view to carrying out this design, I have 



