OF ARTS AND SCIENCES. 3G9 



been obtained in tbe attempt to measure the heat of the stars with the 

 tasimeter. The use of this instrument would be vastly simplified if it 

 was placed on a solid pier near the ground, was not moved during the 

 observation, and could be perfectly prott'Cted from other changes ot 

 temperature than those which it was intended to measure. 



As eitlier of the problems proposed above would occupy the time 

 of a telescope for at least one year, it is obvious that there could be 

 no difficulty in keeping such an instrument occupied indefinitely. 



The horizontal mounting is especially adapted to an elevated position, 

 and would permit the use of a telescope where an equatorial mounting 

 would be quite impracticable. On the other hand, to an amateur, or 

 for purposes of instruction, an instrument which could be set quickly 

 from one object to another, and where the observers need not be ex- 

 posed to the cold, would offer many advantages. The impossibility 

 of observing far from the meridian would be less important with a 

 large instrument, where the number of objects to select from is very 

 great. 



There are certain purposes to which this mounting could not be 

 advantageously applied. The study of close double stars and other ob- 

 jects requiring long examination and very perfect definition could be 

 better left to other instruments. The sun, moon, and planets can also 

 generally be better observed off the meridian. If, however, the entire 

 time of an instrument can be employed to advantage, and it can col- 

 lect several times as much material as an instrument of the usual form, 

 it is no evidence against its trial that there are certain problems to 

 which it cannot be advantageously applied. 



The working force required for such an instrument should consist 

 of at least one observer, an assistant to record, and a number of copy- 

 ists and computers to prepare the working lists, reduce the observations, 

 prepare them for the press, and read and check the proof-sheets. A 

 large volume of valuable observations could thus be produced eveiy 

 year, which would require at least double the time and money to pro- 

 duce by the same telescope mounted equatorially. The difference in 

 the amount of work will be evident when we compare the number of 

 objects observed with a transit instrument per night, with those ob- 

 served with an equatorial. A hundred objects in various declinations 

 might be examined in a single evening, while it is seldom that the 

 same number could be identified and measured by an equatorial in a 

 week. 



VOL. XVI. (n. s. VIII.) 24 



