20 6 Annals of the Philosophical Club 



sharply defined than the disease. The speaker had brought 

 from Breslau the original matter from which the organism 

 was grown, and it had been developed from the blood of 

 an animal, which had died five years before. 



Feb. a8th, 277th meeting. After Dr. Burdon-Sanderson 

 had shown some photographs of the magnified organism, 

 described at the last meeting, Sir J. Hooker produced two 

 pieces of wood, scored and grooved by drifting sand ; one 

 from an old juniper tree (of a species believed to attain the 

 age of 2000 years) which was growing on the crest of a ridge 

 between two valleys at a height of about 9000 feet on Mount 

 Stanford in the Sierra Nevada (North America). The wind 

 blowing across this crest carries with it granite sand, which 

 cuts grooves in the wood, parallel with its direction, and 

 had thus entirely removed the bark, together with an 

 unknown thickness of subjacent wood. The other specimen 

 came from a prostrate limb of a living tree (Pinus albicaulis), 

 growing at an elevation of about 8000 feet on a ridge of 

 Mount Shasta in Upper California. The limb lay in the 

 direction of the prevalent wind ; here the grooves, cut by 

 the volcanic sand, were disposed lengthwise. 



March 22nd, 278th meeting. Dr. Hooker exhibited a 

 specimen of petrified wood, which he had obtained from a 

 museum in Utah, the pores of which contained silver. The 

 origin of the ore is unknown, but large quantities of the 

 metal are said to be extracted from wood of this description. 



Dr. Allen Thomson showed a piece of wood in which a 

 bone of the foot of a large ruminant was embedded ; and 

 several suggestions were offered to explain its presence. 



Dr. Siemens stated that if any motive power, such as that 

 produced by falling water, were expended in generating an 

 electric current, and this, after transmission through a 

 copper rod 2 inches in diameter and thirty miles long, were 

 used to drive a machine, the mechanical effect would be 

 one-half that of the original power. 



April 29th, 279th meeting. Mr. Galton exhibited speci- 

 mens of composite photographic portraits, formed by 

 throwing faint images of the portraits of different persons 



