EIGHTEENTH-CENTURY EXTREMES 255 



" I have put my last hand to my works of this kind, in Pope's 



happily finishing the subterraneous way and grotto. I Twicken- 

 ham, 

 there found a spring of the clearest water, which falls in 



a perpetual rill, that echoes through the cavern day and 

 night. From the river Thames you see through my 

 arch up a walk of the wilderness to a kind of open 

 temple, wholly composed of shells in the rustic manner; 

 and from that distance under the temple, you look down 

 through a sloping arcade of trees, and see the sails on 

 the river passing suddenly and vanishing as through a 

 perspective glass. When you shut the doors of this 

 grotto it becomes on the instant, from a luminous room, 

 a camera obscura, on the walls of which all the objects of 

 the river, hills, woods, and boats are forming a moving 

 picture in their visible radiations ; and when you have a 

 mind to light it up, it affords you a very different scene. 

 It is finished with shells interspersed with pieces of 

 looking-glass in angular forms; and in the ceiling is a 

 star of the same material, at which, when a lamp of an 

 orbicular figure of thin alabaster is hung in the middle, 

 a thousand different rays glitter and are reflected over 

 the place. 



" There are connected to this grotto by a narrow pas- 

 sage two porches with niches and seats, one towards 

 the river of smooth stones, full of light, and open ; the 

 other towards the arch of trees, rough with shells, flints, 

 and iron-ore. The bottom is paved with simple pebble 



