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Coronet, a crown worn by the nobility, An Illustrated Glossary of Technical differing according to the rank of the wearer. Terms used in Architectural and 1. Prince of Wales. 2. Princess Royal.
( Continued from paye 185.) CARTRIDGE PAPER, a thick description of paper of various colours, employed for crayon drawings, cartoons, &c.
Chalk, White, a very common species of calcareous earth, of an opaque white colour, and used, when burned into lime, as the basis of cements. Refined by a peculiar process, it is used in the arts to heighten the lights in drawing on coloured and tinted papers. Black Chalk, also called “drawing slate," is of a greyish or bluish-black colour, is massive, and when broken, the principal fracture appears glimmering and slaty, and the cross fracture dull and fine earthy. It stains paper blackthe streak glistening, and of the same colour as the surface. It is easily cut and broken. Red Chalk is a clay coloured by the oxide of iron, of which, according to Rinman, it contains from sixteen to eighteen parts in the hundred.
COLOGNE EARTH, a colour of a deep brownish tinge. It contains more vegetable than mineral matter, and originates from the remains of wood long buried in the earth.
COMPARTMENT Ceiling, a ceiling divided
COUNTER-GAGE (in carpentry), a method A
used for measuring joints. For example, the
breadth of a mortise is transferred to the water, forming a division between the cyma- place in the timber where the tenon is to be, in tium and crown members, and the lower divi- order to make them fit each other. sion of the cornice, marked A in the engraving.
(To be continued.)
No. 25.-VOL. I.
2. Multiply continually together the two 175.92904 = half sum of two circumf. diameters A B, C D, and the number 11. Divide
the last product by 14, and the quotient will be the area nearly true.
Example.- What will be the area of the ellipse A D B C A, its transverse A B being 15
feet, and its conjugate c p 10 feet? 16 = half diff. of the two diam.
la) 2) 1650
should be a homogeneous mass, and possess a uniform capacity for the reception and retention of the magnetic virtue.
Metalurgists know that lead melts at a low temperature, but if left on a good fire, it gets first a red, and then a white heat; that, continuing to absorb caloric, it ultimately boils at
a uniform heat, which melts gold or silver, as | 7) 825.00
is evident in the process of “cupelation."
Now here we have a specific heat at probably 117.85 sq. ft. = area. 5,000 degrees, and we have also a specific heat
of boiling water at 212 degrees. It therefore 3. Multiply continually together the two struck me, that by heating my needles in boildiameters, and the number .7854, and the ing lead, and cooling them in boiling water, product will be the area of the ellipse.
every particle of the steel would be first raised Example.-What will be the area of an to, and then cooled down to the same temperaellipse, the transverse being 25 inches, and
ture and degree of hardness. The experiments conjugate 18 inches?
have been made with complete success; and more powerful magnets have been made in this
way than were ever made before, without risk 18
1. Magnets weighing 600 grains, and six inches 450
in length, have held in suspension fourteen .7854
times their own weight; and compass-needles 392700
have given by deflection 30 degrees, at twice
their length, from a test-needle. I find that 31416
megnets tempered in this way are not liable to
break, but possess with great hardness a tough353.4300 sq. in. = area.
ness, derived probably from the boiling water. END OY MENSURATION OF SUPERVICES.
Their power of retaining the magnetic energy has for four years remained unimpared, although left without “keepers."
To manufacturers of magnets and makers of New Mode of making Artificial
compass-needles, a knowledge of this mode of Magnets.
tempering steel, at a specific temperature of the heating and cooling ‘mediums, will enable
them to make articles of a superior quality MAKEAs of magnets and compass-needles without risk of failure, or needless expense. know that if the most careful and skilful work- In heating the steel, the bars require to be men be employed in preparing a number of pressed under the surface of the boiling lead magnets from the same steel bar, the magnetic (as the steel would otherwise float on its surpower of the magnets, when compared with face), and the magnet should be suddenly each other, will greatly vary; although every shifted from the lead to the boiling water, the possible care may be taken in forging, temper- instant it has acquired the temperature of the ling, and magnetising, in an uniform way. boiling lead ; for to leave it longer in the lead Experience in these matters convinced me that would spoil the smooth surface of the steel, discrepancies in the 'magnetic powers of mag- and render it as rough as if heated in a furnace nets of the same length, weighi, and quality of or common fire.-William Walker, in Mechanics' steel, arise from the tempering alone; for if | Magazine. the metal be heated in a furnace, or coal fire, one part of the bar may be in contact with
DISCOVERY OF PLATINUM IN FRANCE.-M. glowing coal, another part in flame, a third in heated air, a fourth in contact with coal in a
Gueynard has just informed the General state of ignition, &c.; consequently, the metal
Council of the Isére that he has discovered a is not in all its parts raised to the same tempe
vein of platinum in the metamorphic district of rature, when suddenly removed from the fire
the valley of the Drac, which he hopes to and plunged into a cooling fluid. The relation
work with advantage. Hitherto this precious between the degrees of heat in the heating and
metal, which combines with incomparable cooling mediums is absolutely unknown; mag
hardness the lustre of gold and silver, has only nets tempered in this uncertain way will pos
been met with in the Ural Mountains, and its Jsess different degrees of hardness throughout
Pool scarcity has always rendered the price very extheir length, and their capacity for magnetism
horbitant.--Paris Paper. in all their particles will be unequal and To Make ARTIFICIAL MINERALOGICAL SPARS. luncertain.
-Saturate water, kept boiling, with alum; then Reasoning in this way, it appeared to me, set the solution in a cool place, suspending in that in order to make compass-needles and it by a hair or fine silk thread, å cinder, all steel magnets successfully, we require specific sprig of a plant, or any other trifle ;-as the heats in the warming as well as in the cooling solution cools, a beautiful crystallisation of the process of tempering, in order to insure the salt takes place upon the cinder, &c, which same degree of hardness throughout the steel will resemble specimens of mineralogical|| bars; that is to say, that the metal when cola / spar.