OBSERVATIONS OF LUNAE OBJECTS. 249 



their origin in spots, that they extend from higher to lower ground ; and a 

 third, their sharp and definite character on some occasions contrasted -with 

 their extreme delicacy on others. Mr. Pratt, under date of November 9, 

 1869, wrote as follows : — " As far as I can remember, I have always forgotten 

 to say how delicate the chief parts of the trident are ; they are most delicate." 

 In the Observers' Notes (seepost, pp. 272 to 298) there are numerous instances 

 recorded of the difficulty of detecting the stem and arms of the trident in the 

 neighbourhood of spot No. 1, and often of their complete disappearance. On 

 the other hand, observers frequently speak of the sharp definition of certain 

 streaks. As regards the connexion between the spots and streaks, in the 

 case of the largest spot, No. 1, which is situated on the highest part of the 

 floor, it appears highly probable that the three arms and stem of the trident 

 are connected with it much in the same way as streams of lava are connected 

 with the volcanic orifice from which they issue ; the varying intensity of 

 brightness of the arms is greatly in accordance with the supposition of their 

 being the results of intermittent emanations from an orifice of this kind, of 

 which the cone is spot No 1. The spot ranking next to No. 1 is No. 4, 

 which appears to be of almost the same character as No. 1, the main differ- 

 ence being its frequent hazy appearance, which on some occasions is very 

 marked. Prom this spot three distinct streams appear to issue : — First, the 

 sector, which is usually seen to spread out from it in a fan-shape ; very rarely 

 the fan of brightness has been seen striped, as if the slope from spot No. 4 to 

 the S.E. border were furrowed. Generally the brightness extends as far as 

 the border, where three spots have been (although rarely) seen; and on one 

 occasion a dark space, as if occasioned by a cloud, covered them. Second, 

 the streak »/, extending to the N.E. border : this streak very frequently 

 exhibits, in common with the arms of the trident, a fading of the portion 

 between the cone and the border, so that the portion near the border is 

 usually the brightest. Third, a streak mentioned only as an extension of 

 the sector from spot No. 4 to spot No. 3 ; it is not often seen. The disposi- 

 tion of the three streams indicates very probably the channels in which any 

 ejecta may have descended from the orifice, and in which such ejecta may 

 have so accumulated as to have produced the appearance of "spurs" noticed 

 by Mr. Pratt (see Report Brit. Assoc. 1871, p. 95). On either side N.W. and 

 S.E. of spot No. 4 are the spots Nos. 3 and 6. The three are situated upon 

 the N.E. slope from the " fault," and from No. 3 (which, by the way, is a 

 group of three openings) issues the streak /3, and from No. 6 the streak y. 

 The near parallelism of the streaks /3, rj, and y results most probably from 

 the positions which the spots from which they issue occupy on the sloping 

 ground. 



The north-west part of the floor offers a very decided contrast to every 

 other portion, characterized, as it has been during the two years, by consider- 

 able alternations of brightness, as well as alterations in the forms of the 

 streaks found upon it. The connexion between the spots and streaks, to 

 which attention has been directed, is well marked ; but here in the N.W. area 

 it is difficult to detect such a connexion, if it exists. The principal spots are 

 Nos. 13, 19, and 16 ; and these lie in the principal streak of the district, and 

 do not appear as orifices from which distinct streaks issue. In whatever the 

 peculiarity of this portion of Plato consists, it is one that shoidd be most 

 assiduously watched and every phenomenon witnessed on it most carefuUy 

 recorded. 



The observations had proceeded with great care during a period of more 

 than twelve months, when a new streak made its appearance between spots 



