On the Vitreous Tubes found near Drigg^ in Cumberland. 531 



as a flux on the entire sand heated in the usual manner. The 

 sand so treated is reddened in the first instance, changes afterwards 

 to an opaque white, and finally is very slightly agglutinated, resem- 

 bling in its shades of colour and in its cohesion that which adheres 

 to the outermost coating of the tube. 



The sand was exposed to the flame of a spirit lamp, urged by a 

 stream of oxygen gas, in which flame Dr. Marcet has shewn that a 

 thick wire of platina may be melted. The grains of hornstone por- 

 phyry first began to flow, and presently acting upon the grains of 

 quartz, formed a clear glass mingled with portions of an olive colour. 

 Even thus however the fusion was partial, and the utmost intensity 

 of the flame was required to support it. 



The glass thus formed resembled that of the tube in its external 

 characters, in being very hard and diflScult of fusion, and in contain- 

 ing a great excess of siliceous matter : for it was ascertained that a 

 fragment of the tube was scarcely softened at the edges by the same 

 flame that had melted the sand ; and that the substance of the tube 

 contained a large portion of silica, had been determined by one of 

 the members. 



From what has been stated, it appears that the tubes have all the 

 marks of fusion, and that their substance can be imitated in some 

 measure by subjecting the sand to intense heat. That they are of 

 very recent date is certain from the shifting nature of the sand hil- 

 locks in which they are found, and from their inability to remain 

 alone and unsupported by the sand without breaking. Lightning 

 seems to be the only agent that could at once supply the heat and 

 the force requisite to make them. In "the familiar experiment of 

 perforating a quire of paper by the Leyden battery, a mechanical 

 effect of electricity analogous to the present is exhibited, and in- 

 stances of fusion by the same instrument it is not necessary to enu- 

 merate. 3x2 



