2 REPORT ON 



^ 



where no binnacle could be put, and where the compass was nearly on a level with 

 the top of the smoke-stack. Thus, while at sea, the position occupied by it was 

 almost constantly enveloped in smoke and gas, rendering it absolutely necessary, 

 whenever we left port, to dismount the instrument in order to preserve it from 

 injury. 



Owing to the very short time at my disposal previous to sailing, there was great 

 difficulty in providing proper instruments, but I succeeded in obtaining all that 

 were absolutely necessary. The following is a list of them : 



Portable Declinometer and stand. 



Five-inch Altitude and Azimuth Instrument. 



Dip Circle, with two needles, each three and a half inches long. 



Pair of eight-inch Bar Magnets. 



Pair of eleven-inch Bar Magnets. ^ 



Admiralty Standard Compasses, with stands and deflectors. 



Burt's Solar Compass and stand. 



Prismatic Sextant of six inches radius. 



Mercurial Artificial Horizon. 



Pocket Chronometer, Fletcher, No. 906. 



Silver Comparing Watch. 

 2 Pocket Thermometers. 

 2 Pocket Compasses. 



2 Magnetic Needles, not mounted, each 2.75 inches long, and 0.33 of an inch broad, 

 i Fifty feet Chesterman's Patent Tape Line. 

 i Case of Drawing Instruments. 

 i Gunter's Scale, two feet long. 



The portable declinometer belonged to the U. S. Coast Survey, and was kindly 

 lent by Prof. J. E. Hilgard. 



The small unmounted magnetic needles were intended to be used for measuring 

 the relative horizontal force on shore and at each of the compasses on board ship. 

 For this purpose it was proposed to vibrate one of them on shore, and then taking 

 it on board ship to the compass at which it was desired to measure the relative 

 horizontal force, to remove the compass card from the centre-point, and putting the 

 small needle in its place, vibrate it again. Unfortunately the small needles were not 

 finished till just before we left Philadelphia, and there was no opportunity of trying 

 them till after we were at sea, when, to my great regret, it was found that the jewels 

 were so small that they would not fit on the centre-point of any compass on board, 

 thus rendering them entirely useless. Under the circumstances, for horizontal 

 force on board ship it was necessary to rely entirely upon measures made with the 

 deflectors belonging to the Admiralty standard compasses a method certainly not 

 so convenient, and, owing to the constant swinging of the ship when at anchor, 

 probably not so accurate as counting the vibrations of a small needle. 



The observations on terrestrial magnetism, and for latitude, time, and true bear- 

 ings, were all made by myself and recorded by Mr. Corrin F. Smith, who was cap- 

 tain's clerk on the Monadnock, and acted as my assistant when I was observing. 

 My best thanks are due to him for the efficient manner in which he performed his 

 duties, sometimes under circumstances of very considerable physical discomfort. 



