July 14, 1898] 



NATURE 



261 



reason to be grateful for the efforts made by the Universities to 

 extend these educational opportunities. And stimulus given to 

 the teachers reacts most beneficially upon the schools and pupils 

 under their care. In educational as in all work it is necessary 

 to have patience in awaiting results. The best results of an im- 

 proved system of primary or secondary education are not those 

 which are the first to show themselves. And in course of time it 

 is probable that the number of persons desiring to avail them- 

 selves of opportunities for continuing their education within 

 easy reach of their own homes and in the leisure hours of life will 

 steadily increase. In the circumstances of our own country, where 

 momentous issues of Imperial policy constantly turn upon the 

 popular vote, it is of high importance that we should encourage 

 by all the means in our power the growth of educational organisa- 

 tions which are providing dispassionate instruction in the duties 

 of modern citizenship and diffusing that kind of knowledge 

 which is necessary to the formation of a discriminating judgment. 

 We do not believe that it is possible to indoctrinate busy 

 people with a systematic knowledge of a dozen or fifteen sub- 

 jects, to understand any one of which would require a pre- 

 paratory knowledge of many years. But it is possible to aid 

 intelligent students in every rank of life to gain the elements, 

 the gist, of liberal culture, and to obtain that insight into the 

 vast complexity of human affairs which is the salutary safeguard 

 of intellectual modesty and the best protection against hurried 

 and partial judgments. It is in training and providing the 

 teachers for this great and difficult work of adult popular edu- 

 cation that the Universities are rendering one of their highest 

 services to the country. By equipping and sending out these 

 intellectual missionaries, men of high purpose and of high cul- 

 ture, they are really guiding a national movement. Let us not 

 imagine that great educational enterprises realise themselves 

 mechanically — that the merely fortuitous combinations of County 

 Councils or other public authorities will suffice to secure all that 

 is wanted in the training of citizens for citizenship. Material 

 aid of this kind is indispensable. It is a mark of local interest, 

 it secures the further development of that local interest. But 

 by itself it is insufficient. What is really indispensable is 

 leadership. The man, or group of men, must be forthcoming 

 who, in each centre of population, will take the lead and guide 

 the various forces which are at our disposal into wisely-chosen 

 channels of systematic effort. And it is one of the highest 

 duties of the Universities to train and to send forth such men, 

 to give them moral support in their difficult labours, and to 

 attach to their enterprise the weight of academic prestige. 



SOME CONDITIONS AFFECTING GEYSER 

 ERUPTION} 



The Influence of Hydrostatic Pressure. 

 "DOTH field observation and experiment have contributed to 

 •^ our present knowledge of the physical causes of geyser 

 eruption. The natural history of geyser regions has been sum- 

 marised by Weed {School of Mines Quarterly, New York, 1890, 

 vol. xi. No. 4, p. 289), and the experimental work by Andreas 

 [Neues Jahrbuch fiir Min. Gcol. und Pal., 1893, Bd. ii. p. i). 

 Weed concludes that geysers occur only in acid volcanic rocks, 

 and along natural drainage lines where meteoric waters accu- 

 mulate for discharge. The source of heat is conceived to be 

 escaping hot vapours from slowly cooling lavas, the only known 

 <;eysers occurring in regions of recent volcanic activity. New 

 i;eysers originate by the opening of new waterways along fissure 

 jjlanes in the rock, and such new orifices of overflow are con- 

 tinually forming to compensate the diminution in activity of 

 older vents. The cause of the intermittent spouting which dis- 

 tinguishes the typical geyser was originally stated by Bunsen 

 (Tyndall : " Heat as a Mode of Motion " ; Appleton, 1888, 

 p. 168); the boiling-point of water rises with increased pressure, 

 hence decreases from the lower end of a water-filled tube up- 

 ward. If water of a lower stratum, nearly, but not quite, at the 

 lioiling point, be lifted by the entrance of steam from below to 

 a level of less pressure and lower boiling point, " the heat which 

 it possesses is in excess of that necessary to make it boil. This 

 excess of heat is instantly applied to the generation of steam : 

 the column is lifted higher, and the water below is further 

 relieved. More steam is generated, and from the middle down- 



1 By T. A. Jaggar, jun. (Abridged from the American Journal of 

 Science, May.) 



NO. 1498, VOL. 58] 



wards the mass suddenly bursts into ebullition. The water 

 above, mixed with steam-clouds, is projected into the atmo- 

 sphere. ..." (Tyndall, I.e., pp. 169-170). 



The accuracy of Bunsen's theory was early confirmed by 

 experiment ; and the only mechanism necessary to produce geyser 

 eruption is a tube filled with water, open above and heated 

 below. Many further experiments have been made, however, 

 with a view to explaining the variations observed in the period 

 and interval of geyser eruptions, the relative amount of steam 

 and water, and the effect of artificial stmulants in hastening 

 eruption. Andrece's experiments were directed toward the 

 imitation of Peale's ("U.S. Geological Survey of the Terri- 

 tories, 1884," vol. xii. part 2) types, a classification based on 

 the form of the basins and the relation of the periods of steam 

 and water in the eruption. It is noteworthy that in most of 

 these experiments, the apparatus recommended has an open 

 basin above, which retains the water thrown out and permits it 

 K.0 flow back into the geyser tube. 



In Peale's classification no mention is made of the nature of 

 the geyser-spring during the interval of quiescence ; in some 

 cases there is continuous overflow or discharge, in others there 

 is no overflow except during eruption. As it may be shown 

 that this fact of the presence or absence of hydrostatic pressure 

 at the geyser vent has an important bearing on the conditions of 

 eruption, the writer would suggest a classification based on this 

 very simple distinction ; it is a singular fact that in the published 

 descriptions of geysers this point has been frequently over- 

 looked. If geyser waters represent meteoric drainage, they are 

 affected by the laws of hydrostatic equilibrium. In such case a 

 tube continuously overflowing is in a distinctly different class 

 from one which throws off its waters to join the superficial 

 drainage to the sea only during the period of its occasional or 

 intermittent discharge. The first case is represented by such a 

 geyser spring as " Excelsior," in the Yellowstone Park, a 

 violently boiling cauldron in the hill slope, continually discharg- 

 ing vast volumes of water into the pond below, which in turn 

 drains into the Firehole River ; the Great Geyser of Iceland, 

 and the Rotomahana Geyser (destroyed by the Tarawera eruption 

 in 1886) of New Zealand are other types of the continually 

 overflowing class. " Old Faithful " is the type of the second 

 class ; its waters may be seen in violent ebullition a few feet 

 below the orifice of the vent, but overflow takes place only 

 during eruption. 



Any apparatus designed to imitate accurately either of these 

 must be provided with a supply reservoir having subterranean 

 connection with the geyser tube, by which water may siphon irv 

 to replace that discharged. Obviously this replacement takes 

 place in nature : if the water, as asserted, is meteoric, and 

 governed by the same laws that determine the loci of springs, 

 the natural method of such replacement is by the action of 

 gravity. In the case of Excelsior, this subterranean compensa- 

 tion is continuous ; the effective head of water at the orifice of 

 exit is fairly constant : in the case of Old Faithful the water- 

 column is in equilibrium, and replacement occurs only after 

 each eruption, when this equilibruim has been disturbed by 

 the ejection of the column. 



Experimental Demonstration. 



A simple device to illustrate this process was described by 

 G. Wiedemann {Wiedemann's Annalen, xv., 1882, p. 173) and. 

 mentioned by Andreae {I.e., p. 4). Wiedemann made no 

 geological comparisons, the apparatus having been constructed 

 for class-room illustration in physics ; and most of the geological 

 experimenters have used back-flow apparatus, without supply 

 reservoirs. The essential parts of Wiedemann's apparatus are 

 a water-column heated below, an.d a supply-tube entering this 

 column and connecting it with a reservoir of cooler, superficial 

 waters. When the excess of steam generated has thrown out 

 the main column, cooler water filters in through the supply- 

 tube, and fills the geyser tube to the level of the reservoir. For 

 effective and regularly repeated geyser eruptions, the reservoir 

 level must be* maintained a little below the height of the mouth 

 of the geyser tube. 



The accompanying figure illustrates Wiedemann's apparatus, 

 as it has been used by the writer. The dimensions are as. 

 follows : capacity of each flask, one quart ; length of main 

 geyser tube 4 feet, diameter (outside) 5/16 inches ; diameter of 

 basin 2 feet ; the bottom flares funnel-wise from the centre 

 slightly, and is provided with a J-inch outlet tube t. The 

 lower flask rests on a sheet of wire-netting over the flame of a 



