228 PROCEEDINGS OF THE AMERICAN ACADEMY 



beyond Herschel's stars o and |, these wreaths bend rather suddenly, 

 and tend towards the south-preceding direction. Indications of their 

 presence in this quarter are imperfectly suggested in Lassell's and in 

 Sir J. Herschel's latest drawing. From this point feeble traces exist 

 for 10' or X5' in a south-preceding direction. Their course over the 

 R. Picardiana gives a decidedly reticulated aspect to the whole region ; 

 but, though bright, they are here so closely intertwined and connected 

 by offsets, that it is a matter of no little difficulty to gain a clear com- 

 prehension of their proper relations. The complexity of the details is 

 further increased by several offshoots from this quarter, which cross over 

 into the adjacent R. Derhamiana ; still the general effect is easily re- 

 cognized. 



From the southern corner of the Regio Picardiana, and from those 

 parts of R. Derhamiana and R. Huyyeniana which lie near the Trape- 

 zium on its north-preceding and preceding sides, a number of narrow 

 and bright branches diverge, their extremities tending also to the south- 

 preceding direction. Some of these cross the R. Gentiliana and seem 

 to merge together, forming a nebulous mass, which can be followed 

 through an arc of 10' or 15'. Others, which are less curved, originate 

 near the Sinus Gentilii ; these are nari'ow and somewhat tortuous. 



It is to be noticed that the initial direction of the wreaths {Nehelstrei- 

 fen) changes continuously from an angle of position of 330° on the 

 northern margin of the Sinus Magnus, to one of 220°, or less, at the 

 S. Gentilii, and the sweep of the curve correspondingly diminishes, so 

 that throughout the whole nebulous region preceding the sharply de- 

 fined apex of the R. Huygeniana, the extremities of the filaments have 

 a pretty uniform tendency in the angle of position 220°. As soon, how- 

 ever, as we pass to the fields on the following side of the apex, a change 

 is immediately apparent. The ultimate direction being about in the 

 angle 160°. The principal group of wisps results from the resolution 

 of the R. Messeriana, and the region between the Trapezium and the 

 Proboscis Minor, including both these features, into four or five distinct 

 wreaths having a common initial direction in the angle of position 110°. 

 The very bright nebulosity lying between the S. Gentilii, the Trapezium, 

 and the R. Subnehulosa, cannot be resolved into a regular structure, but 

 three or four condensed spots, constituting the most brilliant part of the 

 nebula close on the south-preceding side of the Trapezium, are plainly 

 distinguished as tufts or curled offsets from a prominent wisp of light 

 which extends from its origin, near the Trapezium, across the R. Gen- 

 tiliana. 



