MS Scientific Intelligence. [Aug. 



inferred from the experiments of Vauquelin, was fully confirmed 

 in Mr. Children's laboratory at Tonbridge. A quantity of oxalate 

 of cerium had been prepared in order to obtain from it the oxide 

 of the metal. This oxalate was exposed in a charcoal crucible 

 within a tobacco-pipe mouth to the strongest heat that could be 

 raised in a forge. In this heat the cerium was volatilized so 

 completely that not the least trace of it remained. 



III. Action of the Agate on Light. 



Dr. Brewster has now established, hy numerous experiments, 

 that the nebulous light of the agate has the same relation to the 

 bright image as the extraordinarily refracted image has to the 

 ordinarily refracted image of all doubly refracting crystals. There 

 is still, however, no appearance of the nebulous light being 

 produced by a higher refractive power than the bright image. 

 AH the phenomena of polarization are produced when the plate 

 of agate is less than the TVoth of an inch ; and the nebulous 

 liirht, when in its evanescent state, can be revived by depolariza- 

 tion with mica, in every respect like one of the images formed 

 by double refraction. The coloured appearances in the agate, to 

 which mineralogists have given the name of iridescence, furnish 

 a series of the most singular results, arising, apparently, from 

 the mechanical structure of different laminae, and seem to open 

 up a new field in physical optics. He is at present examining 

 various specimens, in order to give a greater degree of generality 

 to the results previous to laying them before the public. 



IV. Transition Rocks in Yorkshire. 



I have received the following letter, which I lay before the 

 public; because I consider every fact that adds to our knowledge 

 of the mineralogical structure of Great Britain as interesting. I 

 have myself seen most of the places referred to in the letter, but 

 had no opportunity of determining the structure of them with 

 any thing like accuracy ; nor was I aware that any transition 

 formations occurred upon the east coast of Yorkshire. 



SIR, 



In the Annals of Philosophy, No. VI. Article II. " On 

 Transition Rocks," the writer mentions, that he " knows of no 

 transition rocks to the east of a line extending almost due south 

 from Berwick to the English Channel." 



Knowing from * * * *, and others, that you have visited 

 Yorkshire, and given particular attention to the geology of the 

 county, 1 presume that you are well acquainted with the under 

 stratum of the Wolds, and therefore that the lines I have 

 quoted have escaped your observation, or would have been 



