Dr. Phillips on the Physical Aspect of the Moon. 559 



instrument to an observer interested in the survey of the moon, and 

 willing for a limited time to use his exertions for the accomplishment of 

 a definite object. In my own case I feel sure that this would succeed ; 

 and I believe that my case is essentially that of many intelligent obser- 

 vers of the moon accustomed to extra-meridional observations* 



16. The first desideratum then is an Equatorial Instrument, con- 

 structed with the conditions of ample optical power, — great steadiness, 

 — delicate adjustment, including a sufficient range for latitude,— the 

 usual circular and micrometrical readings, — clock-movement, &c, — 

 so that it may be in every point of view adapted for special obser- 

 vations of the moon (sun, planets, comets, &c. may also be observed), 

 and be available for many years, in the same optical and space-mea- 

 suring condition. According to my view, founded on experience 

 with various instruments, it must be an achromatic, mounted on a 

 transportable solid stand, placed under the roof of a removeable ob- 

 servatory, capable of holding a clock and, if need be, a small transit. 

 The object-glass should be of 6 inches diameter, the focal length 16 

 or 1 7 diameters. 



Such an instrument has actually been made by my direction ; it is 

 finished, and stands complete in the workshop of the skilful artist, 

 whose name is a guarantee of excellence, Mr. T. Cooke of York. Thus 

 the first requisite to give effect to my proposal is practically reached. 



1 7. The second desideratum is that the instrument shall become 

 the property of some scientific body constituted for long endurance, 

 and endowed with so much influence as to be able to give effect and 

 gain adherence to a plan of continuous work, by definite persons, 

 for such periods of time as each in succession may command. The 

 instrument to be confided to each in succession, and mounted in a 

 convenient manner for his use, at his home, during the time 

 appointed. Each observer to furnish, at least once a year, an 

 account of his observations, with drawings on the plan already 

 detailed in the instructions furnished by the Moon Committee of 

 the British Association. At the conclusion of his appointed period 

 of observation, the instrument to be again at the disposal of the 

 scientific body to which it belongs, either to be transferred to 

 another observer, or to be again entrusted to the first observer, ac- 

 cording as may seem best for the attainment of the object in view. 



18. I entertain no doubt that, after the operation of one or two 

 years, each yielding fruit, there will be no other difficulty of obtaining 

 suitable observers than the difficulty of choice among several proper 

 persons, who will be glad to give their services. To remove any 

 difficulty as to the first trial, I presume to offer for the first two 

 years my own services at Oxford ; having already sketched out a 

 definite plan of work, which has not yet been attempted, and which 

 I believe myself able to accomplish. 



19. It would be no part of my plan to take photographs of the 

 moon, but rather to obtain from other observatories the best 

 examples of this kind of work, and devote every available hour to 

 eye-sketching on a large scale of the exact appearance of selected 

 parts of the lunar disk. 



The drawings thus, made, scrutinized and corrected in succeeding 



