SCIENCE-GOSSIP. 



6i 



a volatile alkali which (unless we adopt a very 

 farfetched hypothesis) can he nothing else than 

 ammonia. Argon — so far as it exists at all — is a 

 compound of nitrogen, and, when properly treated, 

 gives ammonia. 



Quite in harmony with Berthelot's observation 

 are the remarkable spectroscopic phenomena 

 described in Science-Gossip in March. The 

 change of spectrum from red to blue when the 

 temperature is raised is as much an indication of 

 decomposition as of mixture, and bears out the 

 observation of the eminent French chemist as to 

 the compound nature of the so-called Argon. In 

 this connection, inasmuch as the spectroscope has 

 played a very prominent part in this investigation, 

 it may be well to recall the pre-eminent service 

 which that admirable instrument has rendered to 

 chemical science during the past thirty-five years. 

 The alkali metals, coesium and rubidium, discovered 

 by Bunsen about the year 1S60, and the metal 

 thallium, which was made known to us by Mr. 



Crookes a little later, were the first trophies of the 

 spectroscope. But for the aid of that marvellous 

 instrument these metals, and also others of more 

 recent date, would have remained buried in the 

 unknown. The spectroscope, however, by reason 

 of its powers in certain directions — its supreme 

 sensitiveness for instance — is utterly unquantita- 

 tive. To use it aright is a work of art and 

 requires genius. We call to mind two instances 

 where the spectroscope has been misused with 

 disastrous results, and we are glad to see that 

 the great experience of Mr. Lockyer has led him 

 to abstain from any hasty pronouncement on 

 Helium, the most recent of the spectroscopic 

 achievements. 



In years' gone by the metal of common lime 

 was mistaken for something new by an operator, 

 and later on two other very eminent men of 

 scienca discovered the apocryphal metal, Jar- 

 gonium. 



New Maiden, Surrey ; April i$th, 1S95. 



GEOLOGY OF THE ISLE OF WIGHT. 



By Thos. Leighton, F.G.S. 



"DROBABLY no area within the three kingdoms, 

 of such limited extent as the Isle of Wight, 

 exhibits so many formations worthy of the attention 

 of the geological student. It may be said, with 

 almost equal truth, that no district receives less 

 attention at the present day ; this in spite of the 

 fact that almost all the beds of the island yield 

 fossils, whilst the sections are almost entirely along 

 the coast, and therefore accessible to everybody. 

 It must not be supposed from the comparative 

 neglect of an interesting district that previous 

 observers have so exhausted the subject that 

 there remain no attractions to the original worker. 

 In spite of the careful observations of the past, 

 unrecorded fossils and new fossil horizons are not 

 difficult to discover, and those who know the 

 island best, look upon it as a promising field for 

 future work. The publication, in 1889, by the 

 Geological Survey, of a revised edition of Bristow's 

 " Geology of the Isle of Wight," by Clement Reid 

 and Aubrey Strahan, has placed in the hands of 

 students a careful and exact statement of all that 

 was then known of the geology of the island, 

 together with lists of all fossils recorded from the 

 different formations, and a complete bibliography. 

 The chief service that such official publications 

 render to geology is that they provide observers 

 with a sure foundation for future work. 



The rocks of the Isle of Wight consist of 

 secondary, tertiary and quarternary deposits, and 



the following table exhibits their several divisions, 

 as generally accepted, in descending order : 



Quarternary, Gravels, etc. 



Tertiary, Oligocene, Hempstead Beds. 

 Bembridge Marls. 



,, Limestone. 



Osborne Beds. 

 Headon Beds. 

 Tertiary, Eocene (Upper), Headon Hill Sands. 

 Barton Clay. 

 Bracklesham Beds. 

 Bournemouth Freshwater 



Beds. 

 Lower Bagshot Sands. 

 (Lower), London Clay. 



Woolwich and Reading Series. 

 Secondary, Cretaceous (Upper), Upper Chalk (with 

 flints). 

 Middle Chalk. 

 Lower Chalk. 

 Chloritic Marl. 

 Upper Greensaiul. 

 Gault. 

 (Lower or Neocomian), Lower 

 Greensand. 

 Wealden. 



The relations between the scenery of a district 

 and the geological phenomena there developed 

 have not infrequently been pointed out. Nowhere 



