1827.] 



Varieties. 



209 



It cleaves readily in a direction perpendicular 

 to the axis of this pyramid, and likewise 

 parellel to planes replacing its lateral edges. 

 It is not transparent, und its specific gravity 

 approaches to that of glauberite, which is 

 2-73. The second, Halfoysite, occurs in 

 more or less regular globular masses, some- 

 times larger than the first, in thoe aggre- 

 gated masses of ores of iron, zinc, and lead, 

 which frequently are found filling the cavities 

 in the neighbourhood of Liege and Narnur. 

 It was first observed by M.Omaliusd'Halloj', 

 in compliment to whom it has been named 

 by M. Berthier. When analyzed by the 

 latter gentleman, its component parts 

 were, silica, 0'395 ; alumina, 0'340 ; water 

 0-265. 



Improved Barometer. Much ingenuity 

 has been displayed in contriving methods 

 whereby the mercury in the cistern of a 

 barometer may be kept at a constant level; 

 floating gages, moveable bottoms, &c., c. 

 have been had recourse to, all more or less 

 objectionable, either from the insufficiency of 

 the means employed, or the difficulty of 

 their application. An extremely simple, but 

 admirable, contrivance of Sir Humphry Davy 

 has supplied the desideratum. The pinion 

 that raises the vernier by which the height 

 of the mercury is led off, depresses at the 

 same time, and in the same degree, into the 

 reservoir, a steel plunger, the size of which 

 exactly corresponds to the interior diameter 

 of the tube of the instrument. 



New White Paint, A colour-manufac- 

 turer in Derbyshire, by name Duesbury, has 

 discovered a mode of preparing from the 

 impure native sulphate of barytes, or what 

 is commoniy known by the name of cawkj 

 heavy spar, ponderous earth, &c., which is 

 found in several parts of this country in large 

 quantities, a material, to be employed as a 

 substitute for white lead in painting, which 

 material, when prepared according to a pro- 

 cess for which he has obtained a patent, is 

 found not to be susceptible of decomposition, 

 or of changing its hue in .situations which are 

 exposed to damp or sulphurous effluvia. Jt 

 is, however more particular!}' designed for 

 water colour than for oil, and when em- 

 ployed on flatted or distempered walls, and 

 as the ground washes, or in the patterns of 

 printed paper hangings, it is found to be a 

 constant white, that is, to retain its snowy hue, 

 unimpaired and unaffected by any chemical 

 action to which a humid atmosphere might 

 expose it. Newton's Journal. 



Artificial Cold. Several methods of pro- 

 ducing artificial cold are generally known, 

 but the following, by the mixture of metals, 

 is, we conceive, a novel result; it is stated, 

 in the Annalesde Chimie,thatM. Dobereiuer 

 dissolved 207 grains of lead, 118 of tin, and 

 284 of birmuth in 1617 grains of mercury, at 

 a temperature of 64 5 of Fahrenheit. The 

 mixture immediately fell to 14 Fahrenheit. 

 Botanical Curiosity. A leaf of the tal- 

 lipot. tree has lately been brought to this 

 MM.Nf-w Scries. VOL. III. No. 14. 



country fron Ceylon, of which island it is a 

 native. The leaf is in a good state of pre- 

 servation ; it measures fully eleven feet in 

 height, sixteen feet and a-h;ilf in its widest 

 spread, and from thirty-eight to forty fet 

 in circumference. If expanded as a canopy, 

 it is sufficient to protect a dinner party of 

 six from the rays of the sun, and in Ceylon 

 is carried about by the natives for that pur- 

 pose. Asiatic Journal. 



Enormous Fossil Vertebra. It is stated 

 in the last number of the Philosophical Jour- 

 nal, that in the neighbourhood of Bridport, in 

 Dorsetshire, a short time ago, a labourer, 

 digging for an ingredient used in mortar, 

 found a vertebra of an enormous animal, 

 larger than that of the whale, and supposed 

 to belong to a land animal. This curiosity 

 is in the possession of a gentleman at Brid- 

 port, who generously rewarded ihe finder 

 with ten guineas. Search has been made 

 after the other parts of the same animal, 

 but without success. The perforation for the 

 spinal marrow is stated to be nearly equal 

 in circumference to the body of a man. 



Strength of Cohesion of Wood. The 

 following results of his experiments on the 

 strength of cohesion of wood have been ar- 

 ranged by Mr. Bevan, in a tabular form, 

 and communicated by him to an eminent 

 scientific journal. Mr. B. having occasion- 

 ally found part of the larger end of the 

 wooden bars drawn out in a cylindrical 

 shape, when the lateral adhesion was less 

 than the longitudinal cohesion, the number 

 of pounds expressive of the cohesion is in 

 these cast's short of what is due to the spe- 

 cimen, and in the table these are expressed 

 by + , as to the other bearing ; sometimes 

 the specimen broke during the motion of 

 the weight, and therefore would have se- . 

 parated under a less force with more time : 

 these are marked 



c . f ,.,r , Specific Cohesion 

 Species of Wood. rfnvKy . Poundg . 



Acacia '85 .. 16,000 + 



Ash -84 .. 16,700 



Ditto -78 .. 19,600 



Beech -72 .. 22,200 



Birch -64 .. 15,000 



Box '99 .. 15,500 



Cane '40 . . 6,300 



Cedar '54 .. 11,400 



Chestnut (horse) .. -61 ,. 12,100 



Ditto (sweet) '61 .. 10,500 



Damson '79 .. 14,000 



Deal (Norway spruce) -34 .. 13,100 + 



Ditto, ditto 17,600 + 



Ditto (Christiana).. '46 .. 12,400 



Ditto, ditto -46 .. 12,300 



Ditto, ditto -46 . 14,000 



Ditto (English) -47 .. 7,000 



Elder -73 .. 15,000 



Hawthorn -91 .. 10,700 



Ditto 9,200 



Holly -76 .. 16,000 



Laburnum '92 . . 10,500 



Lance-wood 1-0 1 .. 23,400 + 



Lignum-vitw 1-22 .. 11.80U 



2E 



