770 



9th. Earthquakes, the registrations of a seismometer. 



A meridian circle of 3 feet diameter, with a telescope of 52 lines 

 aperture, has been ordered from Pistor and Martins ; the Smithsonian 

 Institution has just authorized me to obtain an equatorial of 6 (French) 

 inches aperture, with clock motion, which they will lend me ; in ad- 

 dition to which I have a 48 lines equatorial by Fraunhofer ; these, 

 \vith a clock and one or two portable instruments, comprise my astro- 

 nomical equipment. In magnetism I am most especially desirous of 

 your advice. Pray give me all possible information, and recommend 

 such instruments, times and methods of observation as our limited 

 grant from congress and the number of assistants will enable me to 

 obtain and use as designated. 



Such of the meteorological instruments as v>'e do not possess will 

 be ordered in a few days ; but for a proper seismometer I know not 

 where to go, the onl}' account seen being in one of the eai'lier volumes 

 of the British Association. The instrument is to be obtained at 

 the expense of the Smithsonian Institution, and if you will do us 

 the favour to confer with some of the members of your Association 

 or of the Royal Society who have taken interest in the investigation 

 of earthquakes, you will especially oblige Professor Henry and myself. 

 The opportunity which my residence in Chili will offer to make ac- 

 curate notes of these occurrences may perhaps be productive of use- 

 ful results, 1 do not doubt that the instrument will be ordered the 

 moment I hear from you. 



Whilst I have asked your views especially on magnetism, I shall 

 be grateful for counsel respecting any of the obseiwations which are 

 contemplated, or for suggestions of new series which the locality 

 offers peculiar advantages for making. I have planned this expedi- 

 tion and embark in it with a desire to render the greatest possible 

 amount of useful data to science ; and you may be assured of hearty 

 zeal in whatever yourself or any of the Fellows of the Royal Society 

 may propose. 



Believe me, dear Sir, very respectfully. 



Your friend and servant, 



S. M. GiLLISS. 



Lient. -Colonel Echvard Sabine, R.A., F.R.S. 



