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tion of water flowing from any drainage soils and foliage in very dry seasons has arae, and when possible this should be not been neglected."* determined by measuring the amount flowing off and comparing it with the MONTHLY RATIOS OF FLOW OF STREAMS. recorded rainfall on the known area.

Ratio of

flow. Experiments of this kind are not numer

January

1.65 ous, but from the record of the drainage

February

1.50 of large river and small hill districts in March,

1.65 England,* the flow from the Croton and April.

1.45 Cochituate basins, f the measurements of

May.

.85 June

.75 the Madison and Eaton Brooks, I the fol

July.

.35 lowing percentages of drainage may be

August.

.25 taken as approximately correct:

September

.30 October ..

.45 From mountain slopes or improved

November.

1.20 rock hills...

80 to 90
December.

1.60
woody swampy lands.. 60 80
undulating pasture and wood-

Here unity equals the mean monthly land...

50 : 20 flow, or one-twelfth the mean annual flat cultivated land and prairie 45 60

flow. When the area is ample it will be safe We are now able to estimate the quan. in the calculations to take 50 per cent. tity which can be collected from a given of the mean annual rainfall as collecta- area not exceeding 100 square miles in ble.

extent. Having used as an illustration Having decided upon the percentage thus far this city, we will apply the comof the annual rainfall which can be col- putation to the same locality. lected from the different surfaces, our

The mean annual rainfall here is 36.15 next step is to ascertain its distribution inches, while as shown in Fig. 6, the throughout the year. The average

series of low year precipitation amounts monthly rainfall at Troy, for the last to about .8 of the mean. fifty years, divided by one-twelfth of the The mean annual flow of the streams mean annual fall, will give the ratio of from the drainage area, is assumed to be each month, as follows:

50 per cent. of the annual rainfall.

36.15 X 0.5 +0.8 Jan. Feb. March. April. May. June.

= 1.205 inches. 79 .69 .80 .93 1.06

1.29

12 July. Aug. Sept. Oct. Nov. Dec.

average available rain monthly. 1.35 1.13 1.02 1.19

.96
.82

This average, multiplied by the ratios These ratios may be used in determin. above, gives the depth in inches of availing approximately the rainfall in any able rain flowing in each month, thus: month where the mean annual is known,

Depth in inches but they do not represent the amount

Mean nonthly

Rain flowing flowing from a given area. It will be

Per month. found that when these ratios are the January... 1.205... 1.65..

1.98 greatest the least amount is collectable, February..

1.50..

1.80 1.65.. =

1.98 which becomes evident upon considera- March..

1.45.. =

1.74 tion, that in July and August the tem- May

.85.. =

1.02 perature is high, the evaporation great. June.

.75.. =

.90 est, and the percolation into the ground, July.

.35.. =

.42 and the absorption of vegetable life thé August...

.25.. = .30

.30..

September greatest.

October...

.45.. =

.54 “The analysis of the records of the November

1.20..

1.44 flow of the average Atlantic coast streams December.

1.92 leads to the following approximate esti- which quantities have only to be multimate of the ratio of the monthly mean rainfall that flows down the streams in miles in the water shed to determine the

plied by the number of acres or square each month of the year, in which due amount obtainable. consideration of the evaporation from The fluctuations in the rainfall and in • Beardmore. † Fanning. # Capal Rep., 1863, 1875.

* Fanning Water Supply.

of available

Rainfall.

Ratios.

Х
Х

X X X X

.36

Х

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1.60..

.80

.40

Dec.

.84

1.60

.35

“ AON

.93

1.20

.50

the flow of streams as above shown, From what has been stated it is evitogether with the great variation in the dent that the evaporation from the land consumption, necessitates, in almost and water surface of the drainage area every case, large artificial storage. The has already been taken into account in present article has exceeded greatly the the assumption of only 50 per cent. of limits originally intended, and therefore, the rainfall as flowing in the streams, and the question of consumption will not be this additional loss refers to the reservoir investigated at this time, but before con- surfaces only. cluding it will be necessary to consider briefly the question of evaporation and Collecting the results, we find; the mean percolation, losses which affect largely annual rainfall being...

1.00 the available supply.*

The mean annual of low year series.
Annual available flow of stream..

.50 Experiments in this country on the

Annual evaporation from land and conannual evaporation from water surfaces

sumption by vegetation..... are very limited, but where the depth of Annual evaporation from water surfaces. .60water is ten feet and over, a safe estimate of the evaporation will be about 60 In the calculation upon water works, per cent. of the annual rainfall in the we deal with the monthly ratios as Eastern and Middle States. In the case deduced from the above annual, thus : of Troy, we should have 36.15 +60 per cent. = 21.6 inches. 21.6 inches divided by 12 gives 1.8 inches as the mean monthly evaporation.

This mean must be multiplied by the monthly ratios, as in the rainfall and drainage, to obtain the average monthly evaporation. These ratios are approximately:

Mean ratio. January..

.30 February

.35 March

.50 April.

.80 May.

1.45 June.

1.70 July.

1.85 August.

2.00 September

1.45 October...

.75 November.

.50 December.... The monthly evaporation for this locality would then be closely:

Inches evap. January..

.54 February. March.

.90 April.

1.44 May.

2.61 June.

3.06 July.

3.33 August.

3.60 September..

2.61 October

1.35 November.

.90 December

.63

.95

.45

.75

.30

1.20 1.00

.25

1.70 1.85 2.00 | 1.45

.35

1.08 | 1.12

Feb. Mar. April. May June July Aug. Sept. | Oct.

.75

.35

TABLE OF MONTHLY RATIOS, RAIN FLOW AND EVAPORATIONS.

[blocks in formation]

A MBER.

Translated from "La Nature."

The ancients regarded amber as a pre-was much wrought; medallions, crucicious substance. They made ornaments fixes, reliquaries and images of the Vir. of it, and engraved upon it the images gin being carved in it. of their deities. The Egyptians called The name amber was brought from the it sacal or checheleth. It was one of the East by the crusaders, who got it from three aromas which formed the incense the Arabic wood ambar. The Spanish of the Tabernacle. The Philistines called it ambrara and the Italians ambra. called it sachaleth, and the Phenicians But these names are less significant than secheleth. The Scythians called it savi- those given by the Romans and the Gerum, the Greeks electrum. Chachal sig- mans; the former calling it lapis ardens nifies weeper. Amber, they said, origi- and the latter bernstein, both names sig. nated in the tears of the sisters of Phae- nifying a stone which burns. Modern ton, who were transformed into poplars. Greeks call it berenikenstan. Homer in the Odyssey calls both amber After the treaty of Tilsit, there was and an alloy of gold and silver, electrum. accumulated at the Louvre a large colThe palace of Menelaus was ornamented lection of objects in amber of all shades, with amber.

and wrought in a great variety of forms. The trade of the Phenicians in amber Sicily probably furnished most of the of the north is yet a subject of contro- amber to the ancients, just as at present versy. Herodotus, in his description of the shore of the Baltic supplies the enEurope, makes no mention of amber in tire world. Although amber has been the northern part.

found in small quantities elsewhere, it Tacitus was the first to make mention has up to the present time been chiefly of the amber of Prussia. It was not furnished from these two centers. obtained from Prussia before the year The theory of the origin of amber is 500, but from the peninsula of Cimbria, the following: During the eocene epoch Jutland or the lower Elbe. The amber the present bed of the Baltic was occuwas carried across the continent to the pied by an immense forest, which ex. shores of the Mediterranean. Hatria or tended over most of the northern part of Atria, founded by the Pelagians upon the continent. the shore of the Adriatic, was the cen In dredging at the bottom of the sea, ter of commerce of bronze and amber, there is found, at two meters' depth, and was on the highway between occi. thirty-two species of cone-bearing trees. dent and orient.

These trees exuded a gum, which having The Assyrians engraved ornamental been subjected to long continued pressdesigns upon amber which they called ure in the earth has become amber. The electra or stone of the sun. The Greeks Pinus succinus has produced the larger changed this word to electron. Thales proportion of it. More than twelve was the first to discover that amber, hundred species of fossils have been when rubbed, attracted light bodies; found enclosed in it. When the resin from this fact, as is well known, we get towed from the tree it exhaled an odor the word electricity. The Roman gladi- which attracted flies, and these in turn ators often carried amulets of amber, drew the spiders, who, spun webs to catch bearing the inscription "I shall conquer." them. Reptiles, pursuing their prey,

According to the ancients, amber came were entrapped by it, and a fresh layer from Lydia, where it was formed out of of resin flowing over them, they were the urine of the Lynx, and it was hence preserved for all time. The gum recalled Lyncurium. They knew nothing mained sometines fast to the tree, but it of its nature nor of its vegetable origin. frequently dropped upon the ground and In Byzantine art we find but few objects enveloped shells, minerals, twigs, mones made in amber; but during the Middle and drops of salt water. Ages and throughout the Renaissance it Amber is mined from slight depths in

the earth,* and is gathered by divers and loses its characteristic aspect. If from the bottom of the sea. It is at the surface be scraped with a knife, the times worked up on the shores of the dust formed is heavy and falls; copal, Baltic during storms. Amber is the treated in the same manner, yields a fine property of the crown. In Prussia no dust that floats in the air. one can mine it on his own property 4th. Amber may be bent by smearwithout purchasing the privilege from ing it with tallow, and heating it the government, the income from this for some minutes, taking care to heat it source amounting to 600,000 francs a most strongly at the places where it is year. One company that employs sev- expected to yield the most. The imitaeral steamboats for dredging along the tions will not bend. shores of Konigsberg, pays about 400 5th. Amber is harder than any of its thalers per day for the privilege. imitations. It is with difficulty scratch

The production of amber in 1874 was ed by the finger nail. Copal yields 175,000 kilogrammes, in masses of all easily, especially to repeated efforts. qualities and of all sizes, sent to all 6th. Amber may be cut, sawed, rasped parts of the world. The finer qualities or polished, but cannot be cemented or are employed in the manufacture of soldered as can its imitations. mouthpieces for pipes, cigar-holders, and 7th. To prepare varnish, copal is table and mantel ornaments of all kinds. melted in a copper vessel over a brisk A chandelier of amber made by Hart- fire. At 100° C. the water contained in man, exhibited at Vienna, was bought by it forms considerable steam; the copal the Emperor of Russia for 75,000 francs. melts, preserving its yellow color. Am

True amber is distinguished from sub- ber requires a temperature of 400° to stances which somewhat resemble it, fuse it, at which point it blackens and especiaily copal, by the following char- yields an overpowering odor. acters:

If 33 per cent. of linseed oil be added 1st. Copal is yellow, of a more or less to amber it will melt at 150°. deep tint, but uniform throughout, and 8th. The density of amber is 1.09 to has upon its surface yellow points re- 1.11. The density of copal is 1.04, and sembling crystallized sulphur. Amber, of some false amber, 1.05. on the contrary, in a fragment of 12 9th. Amber yields, upon distillation, centimeters' length will always exhibit a needle-shaped crystals of succinic acid. variation of sbage.

The different copals do not. 2d. If a fragment of amber be rubbed When used for cigar-holders, false amwith the finger in the palm of the hand ber fuses easily; copal cracks while am. for a few seconds, it will exhale a strong ber resists the heat. aromatic odor. Copal and the other The chemical composition of amber is, imitations of amber have not this prop- according to Schrotter, erty.

Carbon 78.82. 3d. By long exposure to the air, amber

Hydrogen 10.25. sometimes parts with its essential oil,

Oxygen 10.90. * The only locality where amber is produced from un. derground works is at Palmnicken, on the Baltic coast. For the brilliant white enamel often The stratum producing. It is the so-called "blue earth,” a loose sandstone of a bluish color, from included glau. applied to fine cards and othe purposes, conite grains, when fresh, but weathering terjers youn the following formula is given: For mation of che district. The thickness varies from 8 to white, and for all pale and delicate shafts and levels, the depth below the surface being about fine, add thereto 100 parts of pure ed. An area of about 160 acres has been proved by shades, take 24 parts by weight of paraf.

kaolin ground being easily excavated by pick and shovel, the (China clay), very dry, and reduced to a advance of the levels is at the rate of 34 10.7.feet in the line powder. Before mixing with the able expenditure of timber is necessary to secure the kaolin the paraffine must be heated to center to center, the roof and sides being lined with it will form a homogeneous mass, which complete door-frame sets, at intervals of 34, feet from fusing point. Let the mixture cool, and the working faces, which, when left to themselves, even is to be reduced to powder, and worked for a short time, readily give way.ne. It is even found into paste in a paint mill with warm them at the change of shift. The section of the levels water. “This is the enamel ready for apvaries with the workable thickness of the bed from 5 to 12 feet in height; the breadth is generally 4 feet. plication.

EXPERIMENTAL INVESTIGATIONS OF THE RESISTANCE

OF FLUES TO COLLAPSE.

By C. R. ROELKER, Engineer Corps, U. S. Navy.

Written for VAN NOSTRAND'S ENGINEERING MAGAZINE.

AND

1. CRUSHING COLLAPSING OF practical value, it is important that the TUBES.- A hollow cylinder exposed to dimensions and the construction of exan external fluid pressure experiences a perimental flues should be, as nearly as circumferential thrust, which has the possible, such as are actually used in greatest intensity at the inner surface of steam boilers; and the experiments the cylinder. When the thickness of should be specially directed to the deterthe cylinder is small, relatively to its di- mination of the quantity of the weakenameter, the circumferential thrust may ing effect of such distortions as may obbe considered, without a sensible error, tain under various conditions of pracas being of equal intensity throughout tice. the wall of the cylinder, and the crush 2. EXPERIMENTS ON THE COLLAPSE OF ing pressure will be given with sufficient TUBES.—The earliest, best known, and accuracy for practical purposes by the most extensive experiments on the re. following formula, viz :

sistance of tubes to collapse were made 2tcc

by William Fairbairn, and were first de. p=

(1) scribed by him in a paper read before d

the Royal Society in 1858. (See “Philowhere p=pressure in pounds per square sophical Transactions,” 1858, also "Useinch, t=thickness of cylinder in frac- ful Information for Engineers,” Vol. II.) tions of an inch, d=diameter of cylin The apparatus used by him consisted der in inches, and C=modulus of rup- of a cast-iron cylinder 8 feet long, 28 ture for crushing of the material. inches in diameter and 2 inches thick,

This formula applies only to the case having a removable cover at each end. of a tube having an accurately circular The cylinder communicated with a force cross section, and constructed through- pump. The pressure within the cylinder out of perfectly homogeneous material, was measured by two spring gauges, which is strained equally at every por- and a safety valve did not permit the tion of its wall. A tube strained by an pressure to rise above 500 pounds per external fluid pressure may be regarded square inch. During the experiments as being in a state of unstable equi- this cylinder was placed upright in a. librium, because deviations from the cir- pit. cular form, either existing originally in The tubes experimented upon consistthe tube or produced by the conditions ed, in most cases, of a single plate, 0.043 under which the pressure is applied, tend inch thick, bent to the cylindrical form to increase in an increasing ratio with the upon a mandril, and riveted and brazed pressure till the tube gives way by col. at the joint to prevent leakage. The lapsing. In practice the cross section of ends of these tubes were riveted and boiler flues is never exactly circular, nor brazed to rigid cast-iron discs. The di. is their material ever perfectly homoge- ameters of these experimental tubes neous, and they always give way by col- were 4", 6", 8", 10", and 12", and their lapsing at a pressure far below that lengths, between the cast-iron ends, given by formula (1). Deviation from ranged between 19 inches and 60 inches. circularity and imperfect homogeneity A pipe, 24 inches in diameter, which in boiler Alues are variable and uncertain passed through the upper cover of the elements, and this fact is sufficient to cast-iron cylinder and was secured to it account for the discordant results ob. by nuts, placed the interior of the ex. tained in many experiments on the col- perimental tube in communication with lapse of flues under apparently equal the outer air. This pipe served also the conditions. To obtain results of real purpose of bracing the upper disc of the

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