.J\'ri(rifii'((fion in Gltiss// hincoii^ Ixocls. (V.V.) 



between the higher and lower layers, similar to tliat seen in the tirst 

 experiment. 



2. ' The Toarcian of Bredon Hill (Worcestershire), and a Com- 

 parison witli Deposits elsevrliere.' liy !S. S. Buckman, Es(]., F.G.iS. 



Tlie Upper Lias (G3) of Brcdon Hill is shown on the Geological- 

 Survey map as more than 300 feel-/ thick, whereas at Wotton-under- 

 Edge it is said to be only 10 feet thick. But at the former 

 locality the Inferior Oolite is represented as resting directly on 

 Upper Lias, while at the latter the ' Midford Sands ' intervene. 

 It is shown that this ' Upper Lias ' at Bredon contains strata of 

 the following hemenie : — Lilli, Variahilis, Struchnanni, Dispansi, 

 Dnmortkria\ and JMoorei, in addition to those of the hemerge Falciferi 

 and Bifrontis, which at \Votton have been called Upper Lias, where 

 the rest have been mapped as the ' Midford Sand.' These sands are 

 210 feet tluck, and hence the Toarcian strata of the two places are 

 220 and 380 feet thick, respectively. Thus the so-called ' Upper Lias' 

 is really the e(]uivalent of the Upper Lias, Cotteswold Sands, and 

 Cephalo2)od-Bed of the Cotteswolds ; of part of the Junction-Bed, 

 the Upper Lias, and Bridport Sands of the Dorset coast ; and of the 

 Toarcian of Xormandy. Measured thicknesses of the strata at four 

 localities in the Cotteswolds are given, and sections to show that an 

 anticline was formed, and penecontemporaneous erosion took place 

 at Birdlip before the 8dssi hemera. A table of comparative thick- 

 nesses of deposits laid down during similar times in the Cotteswolds 

 and Dorset is also given, and a section of the Toarcian at Ma^'-sur- 

 Orne, and of the Toarcian and Aalenian strata at Tilly-sur-Seulles 

 (Calvados), where the Toarcian is reduced to a thickness of only some 

 23 feet. The chronometry of the Toarcian is discussed, and the 

 approximate maxima of deposit formed during the hemerae Falciferi 

 to Moorei are given, amounting to a total of 719 feet. This time is 

 divided into nine hemerae, so that the time-value of a hemera is 

 equal to the average time taken to deposit about SO feet of strata. 

 A concluding table gives the sequence and correlation of the fol- 

 lowing deposits: — The Cotteswold Sands, the Sands at Sodbury, 

 the Midford Sands, those of Cole (Somerset), the Yeovil Sands, the 

 Bridport Sands, and the Northampton Sands. 



3. ' Two Toarcian Ammonites.' By S. S. Buckman, Esq., F.G.S. 



June lOth.— J. J. Harris Teall, Esq., :^LA., F.R.S., 

 Vice-President, in the Chair. 



The following communications Avere read : — 



1. ' On Primarv and Secondary Devitrification in Glassy Igneous 

 Rocks.' By Prot; T. G. Bonuey, D.Sc, LL.D., F.R.S., F.G.S., and 

 John Parkinson, Esq., F.G.S. 



Part I. — By John Parkinson, Esq. 



In this part the types of primary devitrification as found at 

 Obsidian Cliff are briefly reviewed, with the order in which thev 



