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Diameter of calibre,

15 inches. Weight of gun,

49,099 pounds. Weight of shell,

315 “ Charge of powder,

50 " Initial velocity of shot,

1,118 feet. From which we obtain:Height to which the shot will rise in vacuo, 19,530 feet. Force in pounds raised one foot high, 6,051,950. Force compared with the 32-pound shot under a velocity of 1,600 feet a

second, this being taken as 1, 4.80. Force in number of horses working one minute, 186.4. Number of pounds (in shot) raised one foot high by each pound in the weight

of the gun, 125. Next let us examine the 300-pounder coil gun, as constructed by Sir William Armstrong. This is described as follows:Diameter of calibre,

104 inches. Weight of gun,

26,880 pounds. Weight of shot,

300 " Weight of charge,

60 " Initial velocity of the shot,

1,500 feet. From which we obtain the following: Height to which the shot will rise if fired in vacuo directly upwards, 35,156 feet. Force in pounds raised one foot high, 10,546,800. Force compared with a 32-pound shot, being taken as 1, 8.24. Force in number of horses working one minute, 319. Number of pounds raised one foot high (in shot) for each pound of metal in

the gun, 392.

The last gun that I propose to examine is the Armstrong coil gun, throwing a 600-pound shot. Described as follows:Diameter of calibre,

137 inches. Weight of gun,

49,280 pounds. Weight of shot,

600 Charge of powder,

100 6 Initial velocity,

1,400 feet. These elements give the following results :Height to which the shot will rise, if fired in vacuo, 30,625 feet. Force in pounds raised one foot, 18,375,000. Force, a 32-pound shot taken as 1, 14.35. Force in number of horses one minute, 556.8. Number of pounds raised one foot high (in shot) by each pound of metal in

the gun, 372.8. The foregoing facts are comprised in the following table :

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Description,
or Kind of Gun.

Force in Pounds
raised 1 Foot.

Number of Pounds of Shot
Shot under a Velocity of
Force compared with a 32-Ib. Force in number of Horses

| raised 1 Foot by each Pound
1,600 ft. a Second (18 Unity). Working 1 Minute.

of Metal in the Gun.

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It should be borne in mind that the increase of resistance occasioned by rifling is not taken into the account, although it makes an important

item against the Armstrong gung.

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These figures exhibit (in a sensible form) the calibres, and the lengths of the charges of powder, as given in the preceding table, and used

in the Columbiad and Armstrong guns respectively.

Form and proportions intended to be given to a rifled gun by Mr. Treadwell in the year 1863. Experiment alone can determine the choice between the two forms of breech. The President communicated, by title, the following paper, with some remarks upon Mr. Mann's botanical explorations in the Sandwich Islands.

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Enumeration of Hawaian Plants. By HORACE MANN. During a visit to the Hawaian Islands, made for the purpose of studying especially the Botany of the Group, and which extended from the 4th of May, 1864, to the 18th of May, 1865, I botanized over five of the largest of these islands, and brought together a collection which forms the basis of the following Enumeration. In its preparation I have been permitted to examine the other collections of Hawaian plants in the Gray Herbarium ; namely, that by the United States South Pacific Exploring Expedition under Commodore Wilkes, — the fullest hitherto made in these islands ; a set of the specimens gathered by Jules Remy under the auspices of the Paris Museum, given by that institution ; some of Macrae's plants, given by the London Horticultural (now Royal Horticultural) Society; and a few of Gaudichaud's, Chamisso's, Douglas's, and Nuttall's. These materials, and all his own memoranda upon them, were freely offered to my use by Professor Gray, without whose friendly encouragement this enumeration would never have been undertaken, and could not have been accomplished.

The botanists who have collected at the Hawaian Islands, so far as known to me, are as follows:

David Nelson, who accompanied Captain Cook on his third voyage, and collected at the Islands in 1778 – 1779. The plants collected by him are stored at the British Museum, and, excepting a few Labiate, have scarcely been examined until recently.

ARCHIBALD MENZIES, a inost indefatigable botanist and collector, visited the Islands with Vancouver in 1792, 1793, or 1794, or perhaps in each of these years, and made large and valuable collections, mostly on Hawaii. Sets of his plants are in the Hookerian, Smithian, and Banksian Herbaria.

ALBERT Chamisso accompanied Kotzebue in the voyage of Romanzoff, and collected principally on Oahu, late in each of the years 1816 and 1817. He published notes and descriptions of new species in the Linnæa, in conjunction with Schlechtendal. FREDERICK Eschscholtz was the physician of the expedition.

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