public, must be welcome. That this has been achieved is rendered evident by the present remarkable exhibit in Chicago. with cold. The loose end of the metallic W is connected with a system of levers. On the outside, a very light chain hangs to the lever that comes through the wall of the incubator. When the temperature inside the incubator is beginning to exceed the limit for which the apparatus has been set-and this limit can be varied according to circumstances - the W not be touched for these purposes, and thermostat expands, and so works on the The main feature of the new incubator is that it requires no constant and skilled care. It works automatically; both ventilation and heat are maintained without any fluctuations whatsoever, not only for hours, but for days. The incubator need the only attendance necessary is that needed for feeding and washing the infant. The heating is produced by hot water, which circulates in copper piping placed at the bottom of the incubator under the cradle or hammock. This pipe is fed by a water boiler, which stands outside the incubator, and may be heated by an oil lamp, by gas, or by electricity. The temperature is automatically maintained at the required heat by a specially constructed thermostat. This is made in the shape of a W composed of two metals, the one being quick to expand and the other to contract. One side of the W is fastened to the wall of the incubator. The W, thus standing out from the wall, widens with heat and contracts levers that the chain is drawn upwards, and by this action the gas of the lamp is turned down and the supply of heat to the boiler is decreased. The temperature within the incubator consequently begins to go down. The thermostat then contracts, the chain falls, and the gas or lamp is turned on again to the full. Thus, whatever changes may occur outside the incubator, the temperature within regulates itself. So delicate is the construction of this thermostat and the levers attached, that the slightest variation of temperature suffices to set it in motion. Thus the heat within the incubator never varies more than two degrees Fahrenheit, and rarely ever more than one degree. To ventilate the incubator, there is a pipe which is conducted through the wall or window of the house or hospital. Only air taken outside the building is supplied to the infant within the incubator. This pipe, about four inches in diameter, delivers the outside air into a box fastened to the side of the incubator. The air is first moistened and washed by being passed through a layer of absorbent wool suspended over a saucer containing water or an antiseptic solution. A little further on, there is another sheet of wool, which, however, is dry and serves to retain the soot and other particles floating in the air. From this filtering box, a second pipe delivers the air into the bottom and center of the incubator. Just above this inlet, a disc is suspended, which breaks. up the current of air and diffuses it in all directions and over the surface of the hot-water coils. Thus the air is washed, filtered, and warmed before it reaches the infant lying above in the upper part of the incubator, and is uniformly distributed so that there is no sudden current in any one direction. On the top of the incubator, a chimney about three feet long forms the outlet; and in order that this shall not accidentally become an inlet, admitting a downward draught, a revolving screw-fan is placed within this flue, which turns only to allow the outward passage of the upward current. Thus it will be seen that, so long as the lamp or the gas burns, the temperature and the ventilation within the incubator will be automatically maintained. The incubator, being made of glass and metal, can be washed and disinfected with the greatest facility. It is so portable that it can be readily carried from room to room, or placed in a cab and taken to any house wherever required. As no skilled attendance is needed, it can be used in private families as well as in hospitals. So far, incubators have been available only for the rich or the poor. For the great middle class-persons who are not rich, but who are not poor enough to go to public hospitals-there are as yet no incubators available. It is proposed, however, to meet this difficulty. In New York, London, Paris, and other large centers, it is planned to establish incubator stations. In response to a message or a telegram, incubators will be despatched immediately wherever required. This will not occasion any great expense, for the incubators need not be bought. nor will it be necessary to pay for skilled attendants. The incubators will be let out on hire for the number of days they may be required; and thus it may be possible to save the lives of many prematurely born or very delicate infants, for these ingenious machines serve the same salutary purpose in saving the lives of exceedingly feeble maturely born infants as they do in the case of the prematurely born. Ghosts HE burdens that make us groan and sweat; The troubles that make us fume and fret, Are the things that haven't happened yet. Romantic and Thrilling Experience of a Boat Trip Through the Heart of a Mountain-The Strange Course of the River Lesse I' By WILLIAM G. FITZ-GERALD Author of "Round the World," "Travel and Exploration in Central Australia," Etc. T has been said, and with some justice, that Americans "doing" the wonders of the Old World are too apt to rush through the more wellknown centers, and to neglect altogether out-of-the-way places which contain many noteworthy sights in both nature and art. For example, how many Americans, passing through Belgium, and hastily seeing the sights of Brussels, the art treasures of Antwerp, and the Mediaval buildings of Ghent and Bruges-with, of course, a visit to the Field of Waterloo, and a few days on the gay and spacious beach of Ostend-how many such ever penetrate into the wild and beautiful Ardennes country and the great Gorge of the Meuse? Here is a region of fantastic mountain ranges abounding in caves, of which many are unexplored to this day. The visitor may stay in comfort in this region for a dollar a day; and no more restful place could be imagined than the little villages on the Meuse that nestle at the foot of terrific precipices often crowned with crumbling castles and ancient fortresses wreathed in legend and romantic story. From Brussels to Namur is not more than two or three hours; and here the Gorge of the Meuse may be said to commence, the river having in the course of ages wormed itself down among the limestone rocks, which now uprear themselves hundreds of feet, in some places, above its fast-gliding waters. What may be called the center of travel in this region, is the quaint little town of Dinant-sur-Meuse, whose curious-looking houses straggle along both banks of the river, backed by the tremendous limestone precipices whose summits mark the true level of the farm BOATING IN THE HEART OF A MOUNTAIN. Scene on subterranean river.-This chamber towers up 500 feet.-Three hundred feet above the river are the refreshment booths. country, where the language is Walloon -neither French nor Flemish, but an odd mixture of both-are the great caverns or grottoes at Han-sur-Lesse, surely the most extensive series of caves in the world, and traversed for the greater part of their entire length by the river, now become a subterranean stream, and flowing through the very heart of the hollowed-out mountain into which it plunges in roaring cataracts. One takes the train from Dinant station to a place called Éprave, following the course of the Lesse all along through a wildly beautiful country of mountain and waterfall, gorge and forest, with frequent peeps of ruined castles and strong of the river-in other words, the place where the swiftly-running stream plunges into the heart of the mountain under a rugged natural archway of cracked and fissured limestone. The guides here, by the way, speak nothing but their curious. Walloon dialect, and an uncouth kind of French, which is, however, understood by most visitors except the English. One may climb down the green and flowering banks, and even penetrate a few feet into the archway that engulfs the river; but apparently a little beyond, there is an awful precipice. For the roar is deafening, as though the waters had an abrupt descent. The guides absolutely refuse to permit visitors to pass into the THE TECHNICAL WORLD MAGAZINE archway, as many fatalities have oc- Having seen where the Lesse was Woe unto the woman in smart frock and hat who tries to "do" the Great Caves of Han! For what with the steady drip of ice-cold water from stalactites, the mud here and dust there, and unsuspected little pools everywhere, even the veteran climber and walker will emerge into daylight with the river, considerably the worse for wear. It is curious how anxious women are to visit this wonderful series of caves, and yet how little they realize the physical exertion involved. So extensive are these grottoes, so vast and irregular the chambers and saloons, that the complete tour involves four solid hours of walking and climbing. On entering, if the party be small, one is told that the electric light plant is "not working;" and, oddly enough, one is very grateful to hear this, for a reason we shall know later on. It seems the Caves are the private property of the territorial landlord, who also owns the village; and he conducts a regular campaign of advertising by means of picture-posters all over the continent of Europe. The admission fee is somewhat high, about a dollar and a-half; but of course it varies acording to the number of persons admitted at one time. After one has walked and stumbled in the almost total darkness up hill and down dale, a halt is made; and one of the guides produces a magnesium ribbon, sets down his lantern, and presently without a moment's warning a blinding glare of light fills the place, and one beholds for the first time the wonders of this subterranean world. So lofty is the roof that even this powerful light fails to locate it; the bats fly in every direction, hurling themselves blindly against the tites, or the uprising forest of stalagmites enormous snow-white and flashing stalacwhich gleam like so many crystal pillars of some celestial fane. rugged, and minor caves branch off out The walls are wild and fantastically guide, "Have these chambers ever been of them, so that one is impelled to ask the explored?" One is told they have notat any rate, not all of them. It would take years to do this, and would involve much expenditure of time, money, and possibly human life, for sometimes there are abrupt descents with crumbling footholds. finding new wonders in this vast series Exploration is, however, constantly of caves; but unfortunately there are many grottoes which it is impossible to reach, since the only access to them is through holes barely two feet wide. And yet these may lead into stupendous chambers in which the spires of a mighty cathedral would barely touch the roof. It may safely be said that the stalactite and stalagmite masses in the Grottoes of Han are the most wonderful yet discovered; and the mind is aghast to contemplate how many millions of years it must have taken for these petrified masses to names, such as La Cascade, Le Trône, form. Most of them are given fantastic places their almost unearthly purity has La Chaise du Géant, and so on. In many been smirched by candle-flames, smoky oil lamps, and so on; but they remain startling in their beauty when the brilwonders of glistening whiteness, almost liant flash lights up these silent chambers. When the guide arrives at one of these huge "show" groups of stalactite or stalagmite, the visitors group themselves about him, whilst his colleague prepares the magnesium flash. Sometimes tired lady visitors will sit down on the rocks. description in uncouth French. Even the and listen with indifference to the voluble most listless, however, are impressed and wooden hammer from his pocket, and, entertained when the guide takes a striking a needle-like stalactite, awakes reverberating echoes from chamber to chamber, which appear to increase and |