Nullipores dk Sponges of the Boulder Clay of Caithness. 99 



Burn on one of my official visits, I noticed the sections of 

 boulder clay exposed there ; not having time then to devote 

 to their examination, I thought that, although fourteen miles 

 distant from Wick, I would try my pedestrian powers and do 

 so, on the day kept for the Queen's birthday (1855), should 

 the weather prove fine. It did, and I was off early in the 

 morning, so that I might have a long search, not only in the 

 exposed sections of the boulder clay on my route, but every 

 quarry and place of interest. On searching the Burn of Fres- 

 wick, I commenced immediately at the bridge, and in the blue 

 clay there found several flints, evidently from the chalk, 

 hinges and portions of Cyprina, fragments of Turritella, Den- 

 talia, &c, all more or less broken and rubbed. These were 

 firmly embedded, and so were all the specimens taken by me 

 from the boulder clay. After examining the sections above 

 the bridge, I retraced my steps, passed over the road and clown 

 the burn towards the castle, and in a nice section worn by the 

 stream, as well as the usual stones, shells, &c, I met with a 

 white mass, which at first, from its yielding freely to the 

 knife, I thought chalk. After digging it out and washing it 

 in the stream, I was surprised to find that it would swim like 

 cork, and therefore could not be chalk. I put it carefully 

 into one of my boxes, and searched again, and at some distance 

 from the spot where I found the first I got a smaller piece of the 

 same description. They are the only pieces I have met with. 

 I have forwarded the smallest piece with this paper, enclosed 

 in glass, and hope that you will excuse my jealous care in 

 thus preserving the precious relic. As soon as I had fully 

 examined all the exposed clay, I turned my steps homeward, 

 wondering all the way what my swimming prize could be. As 

 soon as possible, after washing and taking my tea, I out with 

 a microscope, and placed a small portion of the mass under it, 

 when, to my delight, bundles of spiculse, and quantities of 

 siliceous globules, were beautifully shown, as well as straight 

 spicula, triradiate, and other shapes ; the spicula hollow in the 

 centre. I fancied it might be a Pachymatisma ; but then 

 the stellate forms were absent. It effervesced freely in dilute 

 muriatic acid. In order to be set right, I forwarded a portion 

 of each piece to Mr Bowerbank of London, who, with his usual 



