382 ANNUAL OF SCIENTIFIC DISCOVERY. 



figured. Dr. Scoresby had the pleasure of being present at the discovery of 

 this particular ibrm in a nebula of the planetary denomination, in which two 

 portions following spiral forms were detected. Its color was peculiar pale 

 blue. He had the privilege, too, of being present on another interesting 

 occasion, when the examination of the great nebula in Orion was first seen to 

 yield decisive tokens of resolution. 



In these departments of research the .examination of the configurations of 

 nebula?, and the resolution of nebulas into stars the six-feet speculum has had 

 its grandest triumphs, and the noble artificer and observer the highest rewards 

 of his talents and enterprise. Altogether, the quantity of work done, during 

 a period of about seven years including a winter when a noble philanthropy 

 for a starving population absorbed the keenest interests of science has been 

 decidedly great, and the new knowledge acquired, concerning the handiwork 

 of the Great Creator, amply satisfying of even sanguine anticipations. 



Dr. Scoresby found, hi September last, that about 700 catalogued nebulae 

 had been already examined, and transferred to the ledger records from the 

 journals of the Observatory (comprising only a selection from the general 

 observations), and the new nebukv, or nebulous knots, discovered merely inci- 

 dentally, amounted to 140 or more. The number of observations, involving 

 separate sets of the instrument, recorded in the ledger (exclusive of very 

 many hundreds, possibly thousands, on the moon and planets), amount to 

 near 1700, involving several hundreds of determinations of position and angu- 

 lar measurements with the micrometer on the far distant stars. The carefully 

 drawn configurations, eliciting new characteristics, exceed 90, and the rough 

 or less-finished sketches amount to above 200. Of the 700 catalogued nebulae 

 already examined, it should be observed that in full one half or more, some- 

 thing new has been elicited. 



In speaking of the effects of the flood of light accumulated by the six-feet 

 speculum of the Earl of Rosse, Dr. Scoresby remarked that this peculiarity of 

 the instrument (connected as it is with due length of focus and admirable 

 definition) enabled it to reach distances in space far beyond the powers of any 

 other instrument. This was its peculiar province ; and in this, as to existing 

 instruments, there was not, nor, as he hoped to show, could there be, any 

 competition. For comparing the space-penetrating power of the six-feet 

 speculum with one of two feet (which has rarely been exceeded) we find it 

 three to one in favor of the largest, with an accumulation of light in the ratio 

 of 6 2 to 2' 2 , or 9 to 1. On comparing the powers of this magnificent instru- 

 ment with those of a refractor of two feet aperture, the largest hitherto 

 attempted, we have a superiority making a due allowance for the loss of light 

 by reflection from two mirrors, and assuming an equal degree of perfectness, 

 figure, and other optical requirements in the refractor, and no allowance for 

 absorption of light in the ratio of about 4/5 to 1, as to light, and as 2*12 to 1 

 as to the capability of penetrating space, or detecting nebulous or siderial 

 objects at the extreme distance of visibility. Hence, while the range of 

 telescopic vision in a refractor of two feet aperture would embrace a sphere in 

 space represented by a diameter of 2 ; the six-feet speculum (assuming both 

 Instruments to be of equal optical perfection, magnifying equally, and allow- 



