348 Clusters, Nebulae, and Occultations. 



with the modesty characteristic of a true philosopher, he admits 

 that his explanation is not very satisfactory. 



As might be expected, these canals are very difficult teles- 

 copic objects, and perfectly hopeless with small apertures. I 

 should never have thought of looking for them but for Secchi's 

 valuable piece of information, that the first or innermost 

 canal is the apparent exterior boundary of the nebula in small 

 instruments, as well as his statement that the 6i- inches of the 

 Cauchoix achromatic at Rome were sufficient to show the first, 

 with as much of the nebula beyond it as reaches to the second 

 canal. Thus instructed, I attacked the object, a good while ago, 

 with my 54 inches, but so entirely without success that I 

 never repeated the attempt till the memorable night of the 

 earthquake, when, the atmosphere being clear, notwithstand- 

 ing rather flaring definition, I detected, with a comet eye-piece, 

 power about 29, as well as with a higher power of 64, the 

 lighter tract between the two canals, like a riband of the thin- 

 nest gauze drawn over the dark sky, parallel for some 

 distance to the edge of the main body of light, but separated 

 from it by the innermost of these open spaces. Faint as the 

 object was, even as a mere suspicion, and utterly undiscoverable 

 except from previous knowledge, to my great pleasure it was 

 unquestionably there. I then perceived at once the inaccuracy 

 of the expression that Bond had discovered these canals in the 

 nebula, unless it were at the same time stated that he had 

 given to it a previously unsuspected extent, — what he calls the 

 axis of the nebula being nearly the whole of it as visible in 

 inferior instruments, — and that these features were to be 

 sought outside of the nebula as commonly seen, in the newly 

 detected part. I became aware at the same time but too 

 plainly with how much justice Secchi has criticised Bond's 

 figure, as giving too much strength to the light between and 

 outside of the canals ; a remark made also by the Earl of 

 Rosse's assistant with the 3 -feet reflector ; in fact the engrav- 

 ing docs not correspond with the attendant description, that 

 " the liofht between them is two-thirds as bright as it is on the 

 inner side of that which is nearest to the nucleus," siuce it 

 has been made to appear sensibly equal. In my telescope the 

 difference is extreme; the aperture being only just sufficient 

 to make the feeble ray perceptible, at least to vision such as 

 mine. 



In other respects, too, Bond's figure is unsatisfactory, the 

 proportional light of the two companion ^nebuhe being far from 

 accurately given ; its defects, however, have been greatly ex- 

 aggerated in some of the copies, and that given by Arago, if it 

 is to be considered as a copy at all, bears so little resemblance 

 either to the original or to nature that, without a name, it 



