Feb. 23, 1883.J 



♦ KNOWLEDGE ♦ 



121 





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SPKIXGS AND STREAMS. 

 [727] — Having made a large number of observations on the phe- 

 ■omenon of springs, I hope to be able to throw a little h'ght on 

 "Zeta's" inqniries. 



1. I have not found that springs are affected by the direction of 

 the wind, but I have found that their rise and fall is coincident with 

 that of the mercury in the barometer, only in opposite directions, 

 that is, with a falling barometer a strengthening spring, and vice- 

 Tersi. 



2. " Quick rise after low, foretells stronger blow," and also 

 treqnently rain. In the case of a spring the order is reversed. 



S. If springs continue to fall after heavy rain, it shows that the 

 rain has not percolated to the water-line, but that that part of the 

 lainfall which has not gone off by evaporation has been retained in 

 the strata lying above the lino of saturation, by capillary or other 

 attraction. 



In order that the foregoing remarks might be better understood, 

 let tu take a walk in a southerly direction from the Thames, select- 

 iag a valley — say that of the Wandle. We pass over London clay of 

 eoomderable thickness, and abo.it three miles from the Thames find 

 • number of artesian wells, the water from which is obtained by 

 boring through the lower eocene formations, into the chalk, when 

 the water rises to the surface and continuously overflows; indeed, 

 in one case the water may be seen flowing from the mouth of the 

 iron pipe— with which the well is lined — at a height of ten feet 

 above the ground-level, its fall being utilized in turning a small 

 wheel used for grinding purposes. 



Careful observations in a well of this description show that the 

 flow is immediately affected by the atmospheric pressure, a fall of 

 one inch in the mercury being accompanied by an increase of about 

 S per cent, in the flow of the spring. 



Continuing our walk southwards, we soon arrive at the foot of 

 the Surrey hills, where numerous beautiful springs are thrown out 

 •t the contact of the Thanet sands with the chalk, where the point 

 of contact lies low. The water does not, however, rise in a vertical 

 direction, but moves forward in a nearly horizontal plane from the 

 ■lain body of the chalk. Let us continue our walk up the hill, 

 ■neaetiring the depth to the water in all wells met with ; and also 

 with an aneroid, note the level of the month of the well. On our 

 ntnm we plot a section of the ground passed over, and mark in 

 the wells with the water-line. The chalk above this line is 

 partially, and that below thnroughiy, saturated. Above the line, 

 'he water particles move downwards perpendicularly; below, the 

 »'ater moves forward slowly to the point where it re-appears as a 

 ispring, after years of disappearance since it fell as rain ; part, 

 however, passes under the London clay and re-appears lower down 

 ■lie valley in the shape of an artesian well (overflowing well would 

 be more exact). 



It is the water lying above the point of saturation that is affected 

 by the atmospheric pressure, and from which the water below the 

 line of saturation receives an accession, even at times when there 

 ■3 no rain ; with a rise in the water-line, there is also an increase in 

 the flow of the springs, and vice-versa. 



There is ordinarily a great pulsation of the water-line annually ; 

 the rise due to the autumn rains commencing about Christmas, and | 



attaining its maximum about Midsummer, the full being from that 

 time to Christmas. The )>criods of rise and fall will, of course, 

 depend mainly on the time and nature of the rainfall, but that 

 given is as a broad rule correct. (" When the days begin to 

 lengthen, the springs begin to strengthen.") This is the reason 

 why deep-seated springs are often stronger in summer than in 

 winter. 



A number of subsidiary pulsations in the water-line, however, 

 occur, due, as before stated, to tho variations in the atmospheric 

 pressure. Why this should be so, however, is more difficult to dis- 

 cover. Take the case of a well on a chalk hill, where we measure 

 down 200 ft. to the water-line. If wo take a column of chalk from 

 its side one foot square, and extending from the top to 10 ft. below 

 the water-line, we have 200 cubic feet partially, and 10 ft. totally 

 saturated. In tho latter case, the volume of water contained in one 

 foot of chalk will be about two gallons, while in tho latter it varies, 

 but I have found damp chalk, that is, partially saturated chalk 

 only, to contain IJ gallons per cubic foot. In our column, then, 

 we have 200 x 1} =300 gallons, or an ample supply from which that 

 below can bo replenished if suitable means be adojited. Nature's 

 means arc the rise and fall of the atmospheric pressure, although, 

 as I unfortunately do not jiossess an air-pump, I am unable to state 

 the exact way in which this is accomplished. 



Incidentally the rain-fall is about 30 in. per annnm in our case, 

 two-thirds of which do not become absorbed by the chalk, but are 

 lost by evaporation, and by being taken up by plants, &c. It 

 would take fifty-eight years, therefore, merely to partially saturate 

 our column. How long, therefore, does it take the rain falling to- 

 day to reach the water-line, although its effect might be seen a few- 

 weeks hence only? Chalk. 



[728] — In the Tenth Annual Report of the Commissioners of 

 Inland Fisheries, U.S.A., page 6i, is tho following (1809) : — In the 

 autumn of 1808, the Commissioners established a small batching 

 house at Maple Spring, in Wareham. Daily observations of the 

 temperature of water and air were recorded, and there appeared 

 thence a fact which seems never to have been explained, namely, 

 that tho temperature of spring water falls before a storm without 

 regard to the rise or fall of the surrounding air. Thus on Nov. 20, 

 1868, the air rose 1° and the water fell 5'. This fall was imme- 

 diately followed by the greatest gulo of the year. Similar phe- 

 nomena were noted both in 18CS and 1807. C. W. Haedixg. 



TELESCOPES AND MICROSCOPES. 



[729]— In Knowledge (Jan. 13, 1883, p. 28), in an article by 

 Mr. T. Foster, on Mercury, I read this passage ; — " I have seen it 

 stated — nay, proved, if the writer who made the statement can be 

 trusted — that the ancient Assyrian astronomers knew all about the 

 rings of Saturn, the four moons of Jupiter, and other astronomical 

 wonders which only the telcscoiie could have revealed to them." 

 What evidence, may I ask, is there that any ancient people possessed 

 artificial means of assisting natural vision ? I have always thought 

 there must have been some scientific aids, but I never heard of any 

 glass lens — imperishable as glass is — or other object having been 

 discovered in the dihris of the past, that could have answered any 

 such purpose. It seems incredible that the Assyrians, the Indians, 

 the Arabians, the Egyptians— to say nothing of the Greeks, their 

 pupils — should have made the observations of the heavens they 

 did without artificial, that is, scientific, aid. Ennins, according to 

 Cicero, puts into the mouth of Iphigenia the following speech to 

 reproach Achilles with his superstition and cruelty : — 



" Astrologorum signa in ca-lo qua-rit obscnrat Jovis, 

 Cum capra aut nopa aut exoritur nomcn aliquid belluarnm. 

 Quod est ante pedes, nemo spectat, cceli scrutantur plagas," 

 and Socrates, according to Plato, used to tell a story of Thaks 

 tumbling into a well wliilst studying the stars. 



Now, although I by no means say that poets are the best 

 historians or astronomers, it is plain tho starry heavens were 

 eagerly scanm^d, and strange animals discovered or fancied. How ? 

 The modern telescope, if I mistake not, is attributed to Janscn, who 

 lived in the sixteenth century, and it waa brought into notice by 

 Galileo, who got into trouble by seeing further with it than the 

 priests of his church conld. 



Now as to the microscope, "qnod est ante pedes, nemo spectat" 

 is not quite correct, for it is plain Epicurus and tho Greek philo- 

 sophers examined primordial atoms with a searching, critical 

 eye : — 



" Sunt igitur solida primordia simplicitate, 

 QncB minimis stipata cohaerent partibus arete," &c., Ac. 

 (Lncr. de Rerum Nat. I., 603) ; and if it be again objected that 

 poetry is no proof, Pliny senior, a little later, must have examined 

 nature pretty closely and (excuse me) prosily. But how ? With- 

 out artificial assistance ? The invention of the microscope, like the 



