Curiosities of Science. 235 



furnished a succulent food to the fish. Meanwhile the' Valisperia plants 

 absorbed the carbonic acid exhaled by the respiration of their compa- 

 nions, fixing the carbon in their growing stems and luxuriant blossoms, 

 and refreshing the oxygen (during sunshine in visible little streams) for 

 the respiration of the snails and the fish. The spectacle of perfect equi- 

 librium thus simply maintained between animal, vegetable, and inor- 

 ganic activity, was strikingly beautiful ; and such means might possibly 

 hereafter be made available on a large scale for keeping tanked water 

 sweet and clean. Quarterly Preview, 1850. 



HOW TO IMITATE SEA-WATEE. 



The demand for Sea-water to supply the Marine Aquarium 

 now to be seen in so many houses induced Mr. Gosse to at- 

 tempt the manufacture of Sea-water, more especially as the 

 constituents are well known. He accordingly took Scheveit- 

 zer's analysis of Sea- water for his guide. In one thousand 

 grains of sea-water taken off Brighton, it gave : water, 964*744; 

 chloride of sodium, 27*059 ; chloride of magnesium, 3*666 ; 

 chloride of potassium, 9*755 ; bromide of magnesium, 0'29 ; 

 sulphate of magnesia, 2*295 ; sulphate of lime, 1*407 ; carbon- 

 ate of lime, 0*033 : total, 999*998. Omitting the bromide of 

 magnesium, the carbonate of lime, and the sulphate of lime, as 

 being very small quantities, the component parts were reduced 

 to common salt, 3 oz. ; Epsom salts, oz. ; chloride of mag- 

 nesium, 200 grains troy ; chloride of potassium, 40 grains 

 troy ; and four quarts of water. Next day the mixture was 

 filtered through a sponge into a glass jar, the bottom covered 

 with shore-pebbles and fragments of stone and fronds of green 

 sea-weed. A coating of green spores was soon deposited on the 

 sides of the glass, and bubbles of oxygen were copiously thrown 

 off every day under the excitement of the sun's light. In a 

 week Mr. Gosse put in species of Actinia Bowerlankia, Cellu- 

 laria, Serpula, <fec. with some red sea-weeds; and the whole 

 throve well. 



VELOCITY OF IMPRESSIONS TRANSMITTED TO THE BRAIN. 



Professor Helmholtz of Konigsberg has, by the electro- 

 magnetic method,* ascertained that the intelligence of an im- 

 pression made upon the ends of the nerves in communication 

 with the skin is transmitted to the brain with a velocity of 

 about 195 feet per second. Arrived at the brain, about one- 

 tenth of a second passes before the will is able to give the com- 

 mand to the nerves that certain muscles shall execute a certain 

 motion, varying in persons and times. Finally, about 



A slight electric shock is given to a man at a certain portion of the skin ; 

 and he is directed the moment he feels the stroke to make a certain motion, as 

 quickly as he possibly can, with the hands or with the teeth, by which the time- 

 measuring current is interrupted. 



