272 Worhfor the Telescope. 



will be rippled over, as it were, as though, they lay at the bottom 

 of a rapid stream ; at another, " flares" and distortions of 

 various kinds and degrees will task the observer's patience, 

 if they do not wholly frustrate his expectations. It is almost 

 impossible to form a conjecture beforehand as to the prospect 

 of a good night. Easterly winds have borne perhaps a heavier 

 share of blame than they deserve ; at least, I have noticed that 

 when we have a ivarm breeze from the N.E., it usually brings 

 sharp definition : and Herschel II. speaks of three nights of 

 unexampled perfection (March 28, 29, 30, 1830), as ushered in 

 by an east wind. His illustrious father states that dry air is 

 unfavourable ; frost sometimes favourable, sometimes not ; thaw 

 may be expected to be unfavourable, from the conflict of cooler 

 and warmer currents. But, strange as it may seem, the un- 

 varying experience of observers speaks strongly in behalf of a 

 slight fog or haze, not, of course, for the detection of evan- 

 escent points of light, but for that steady definition which, with 

 large apertures especially, is so seldom to be met with, and so 

 very beautiful when it is attained. It would be easy to cite in- 

 stances. Sir J. Herschel, speaking of March 28, 1830, says, 

 " such a night for measurement I never witnessed, yet to the 

 naked eye the stars are very dull {stellis acies outusa), and no 

 small ones (below 4' 5 mag.) visible •" and the new dusky ring of 

 Saturn was discovered by Bond, in America, in a sky so hazy 

 that to the naked eye only the brighter stars were perceptible. 

 Herschel I. states that vision is generally very perfect in windy 

 weather; but a very steady stand will be necessary to avail 

 ourselves of it. In the winter, his son tells us that distinct 

 vision often comes on an hour or two before midnio-ht. It is a 

 singular fact, but attested by the concurrence of mam'- observers, 

 that a twilight sky is often favourable to the definition of diffi- 

 cult objects ; the spurious discs seeming to be diminished upon 

 a brighter background. 



The objects in the following list are numbered for con- 

 venience of reference, but no regular arrangement has been 

 adopted ; the easiest and most instructive take the lead, but 

 any stated classification would be too much complicated with 

 considerations of absolute and relative magnitude and distance, 

 and would have to be subordinated after all to the season of 

 observation, which will cause the postponement of many pairs 

 otherwise entitled to precedence. For the student's conve- 

 nience the present series has been restricted to objects visible 

 with the naked eye, and in easily recognized positions, as well 

 as within the reach of ordinary telescopes ; the directions given 

 for finding them will probably supersede the use of maps ; but 

 should such illustrations be desired, the Larger Star Maps of 

 the Society for the Diffusion of Useful Knowledge, sold by 



