HARDWICKE'S SCIENCE-GOSSIP. 



229 



many shapes. There is no difficulty in tracing all the 

 forms of the hydrocaulus of P. scotica up to the varied 

 shapes which these branchlets assume. In their 

 natural state — that is, when attached to the side 

 branches — these appear somewhat different to the 

 figures given by Dr. Duncan in the "Philosophical 

 Transactions ;" but whenever they are broken away 

 from the branches, a small portion of the poriferous 

 face of the branch is broken off with them, and then, 

 ■when found unattached in the shale, they present the 

 same characters as the hydrocaulus and trophosome 

 given by Duncan — except the hollow character shown 

 in one of his figures. On looking at the figs. 171 to 

 174, all the branchlets seem to be thrown off without 

 any expense to the colony. But this is a false idea. In 

 the study of Fig. 205, Science-Gossip, Nov. 187S, 

 it will be seen that there has been general disarrange- 

 ment in several branches ; and the formation of the 

 fenestrules has suffered in consequence of the forma- 

 tion of these branchlets. This specimen has been 

 slightly rubbed down* for the purpose of tracing the 

 connection between the branch and the branchlets. 

 At {a) the bases of the cells are somewhat exposed, 

 and at (b) there is an immature fenestrule, and on the 

 reverse side there are the remains of P. scotica, as 

 figured in 205-6. It is not only on the zocecium that 

 the "non-sexual" reproduction devolves, but appa- 

 rently, from what is shown here, upon the zoarium 

 also. This is no solitary example of the production 

 of Palreocoryne. I have many of a similar character ; 

 and I have found, generally, that wherever there is a 

 disarrangement of the ordinary shape of the fenestrule, 

 Palceocoryne in some of its forms is the disturbing 

 agent. On the face there is a contraction, or some- 

 times a cohesion of branches, while on the reverse 

 there are the bases apparently, but apices in reality, 

 of P. scotica. In one of my specimens (Fig. 176) from 

 the Halkyn carboniferous shales, the character of 

 both P. scotica and P. radiata are preserved. To 

 show this with more truthfulness, I have drawn a 

 portion of the reverse of the Fenestella, and several of 

 the fenestrules. At (a) a portion of the branch is 

 withered, but this part of the trophosome is appa- 

 rently in sittc ; at (/') also the base of the hydrocaulus 

 is broken away from what Dr. Duncan calls the 

 tentacular surface of P. radiatum. In Figure 203, 

 Science-Gossip, 1878, we have an organism 

 altogether different from anything that has been 

 figured or described, and I have striven to give the 

 general as well as the true character of the specimen. 

 The apparent organism is seated astride a fragment of 

 Fenestella. But this hitherto undescribed form is not 

 Palseocoryne. 



In Fig. 175, a specimen from Richmond in York- 

 shire, I have ^iven the hydrocaulus of P. scotica, 

 similar in some respects to the figure of Dr. Duncan 

 in the "Philosophical Transactions." I give these, 



* " Rubbed down," not " upside down " as in description. 



not because they are rare, but as species that are very 

 plentiful. Of these I have several score, and I have 

 studied them in all the gradations from one form up 

 to another, and although my cabinet is enriched by 

 specimens from Yorkshire, Northumberland, Belston- 

 burn, Gare, and Hairmyres, in fact, from nearly 

 everywhere where Fenestella is found, still the whole 

 present the same type— the character of the Belston- 

 burn and Gare series coming nearest to the Yorkshire 

 series, and those from Hairmyres comparing favour- 

 ably with those from Northumberland. 



( To be continued.) 



THE ARCHED CROWN ; MOTION OF 

 CLOUDS ; SPIRAL CURRENTS. 



By the Rev. S. Barber, F.M.S. 



THE phenomenon of repulsion between cloud- 

 masses of apparently different composition, to 

 which we drew attention in Science-Gossip for 

 January 1879, as instanced in the case of the 

 "arched crown" over the summit of cumulus, sug- 

 gests to us this inquiry : how does it happen that in 

 an apparently homogeneous state of the surrounding 

 air, the visible vapour or cloud can assume such 

 varieties of form, and develope new physical pro- 

 perties ? 



In order to facilitate our conception of cloud 

 phenomena, and to help us to understand the laws 

 which affect them, it is well perhaps to regard the 

 watery atmosphere as distinct from the composition of 

 oxygen and nitrogen by which it is surrounded, and 

 in which it passes through its protean metamorphoses. 

 To consider a cloud as a thing isolated and distinct 

 from the air which encloses and to a great extent 

 permeates it, may not be altogether a philosophical 

 method of regarding the subject ; but undoubtedly 

 it has a basis of truth, and is useful in respect to 

 weather study. And inasmuch as various species of 

 cloud possess peculiar thermal and electrical proper- 

 ties, it is not entirely unscientific. 



We are therefore justified probably in regarding 

 the principal forms of cloud as organisms, actuated 

 by certain laws and exercising peculiar forces ; playing 

 in fact, an important role in the economy of Nature. 

 Thus we may realise the conception of the poet, as 

 embodying not only the ideal beauty, but also some- 

 thing of the physical truth of his subject, when he 

 represents to us the cloud as a beneficent angel : 



" I bring fresh showers for the thirsting flowers." 

 And again, 



" I wield the flail of the lashing hail." 

 To give a satisfactory explanation of such electrical 

 phenomena as the " capped cumulus " is, indeed, no 

 easy task ; but a better account might perhaps be given 

 of them if aeronauts would provide themselves with 

 instruments of sufficient delicacy : yet the appear- 

 ance of the sky alters so much with distance that 



