176 ANNUAL OF SCIENTIFIC DISCOVERY. 



mented in the denser tissues; that the air must come from the larger tubes, 

 which cannot serve for the ascent of the sap. 



It is plain that the evident tendency of all these experiments is to explain 

 the ascent of the sap in vegetables by capillarity. The idea is not new, but 

 it has not been hitherto fully admitted, notwithstanding the experiments 

 which have been heretofore made. 



Jamin gives it probability in showing by decisive experiments that porous 

 bodies exercise a capillary action superior to the pressure of the atmosphere; 

 further, he gives the physical theory of capillarity in porous bodies, and 

 succeeds in calculating the phenomena of the movements of liquids in trees. 

 Correspondence of M. tickles with Silliman's Journal, May, I860. 



STRENGTH OF ICE. 



Recent experiments in Germany show that when the thickness of ice is 

 an inch and a half, it will just bear the weight of a single man; when about 

 three inches and a half, it will bear detachments of infantry, with their ranks 

 rather wide apart; with a thickness of four and four-tenths inches, eight- 

 pounders can be conveyed over it on sledges; five and two-tenths inches will 

 bear twelve-pounders; eight inches will bear twenty-four-pounders ; and a 

 thickness of twelve inches will bear almost any Aveight. 



SHOWER OF ICE. 



Captain Blakiston, in a letter to General Sabine, which has been communi- 

 cated to the Royal Society, dated H. M. S. Simoon, Singapore, 22d of 

 February, 1800, gives an interesting account of a shower of ice which fell 

 upon the ship. He says : " On the 14ih of January, when two days out 

 from the Cape of Good Hope, about three hundred miles S.S.E. of it, in 

 latitude 38 53' S., longitude 20 4-3' E., we encountered a heavy squall, with 

 rain, at ten A.M., lasting one hour, the wind shifting suddenly from east to 

 north (true). During the squall there were three vivid flashes of lightning, 

 one of which was very close to the ship, and at the same time a shower of 

 ice fell, which lasted about three minutes. It was not hail, but irregular- 

 shaped pieces of solid ice, of different dimensions, up to the size of half a 

 brick. The squall was so heavy that the topsails were obliged to be let go. 

 There appears to have been no previous indication of this squall, for the 

 barometer at six P.M. on the two previous days had been at 30.00, the .ther- 

 mometer 70; at eight A.M. on the 14th the barometer marked 29.82, the 

 thermometer 70; at ten A.M., the time of the squall, 29.80, the thermometer 

 70; and at one P.M., when the weather had cleared, wind north (true), 29.7(3, 

 thermometer 69; after which it fell slowly and steadily during the remainder 

 of the day and following night. As to the size of the pieces of ice which 

 fell, two, which were weighed after having melted considerably, were three 

 and a half and five ounces respectively; while I had one piece given me, 

 a good quarter of an hour after the squall, which would only just go 

 into an ordinary tumbler; and one or two persons depose to having seen 

 pieces the size of a brick. On examining the ship's sails afterwards they 

 were found to be perforated in numerous places with small holes. A very 

 thick glass cover to one of the compasses was broken. Although several 

 persons were struck, and some knocked down on the deck, fortunately no 

 one was seriously injured." 



