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did not exceed 25,000 or 30,000. De Candolle modified his plan, and took up the series of families under a very much abridged form in his work which he called the Prodromus. The title indicates that he at some future time hoped to take up again the Systema, but the enormous increase in the number of species discovered, after the peace of 1815, soon convinced him that this was impossible, and as the articles in the Prodromus were considered too brief, he lengthened the descriptions, after the third volume, and continued to do so until the middle of the seventh volume. There he came to the end of the great family of compound flowers, the elaboration of which was his last and greatest effort.

He was attacked by a serious illness just as he attained his sixtieth year, and was obliged to accept of assistance in the work of continuing the Prodromus, which he had never before done, except with articles of very little consequence. MM. Bentham, Dunal, Decaisne, Grisebach, Choisy, Duby, Boissier, Moquin, Meissner, and Alphonse de Candolle contributed their aid, and gradually furnished extended articles. De Candolle expired on the 9th of September, 1841, and his son continued to direct the Prodromus, preparing himself certain articles. With the aid of other assistants, at the end of thirty-two years he had added ten volumes to the seven that his father had published. The seventeenth volume completed the principal class of the vegetable kingdom, the Dicotyledons, with the exception of one family (Artocarpeis) which the author could not prepare in time, notwithstanding the delay accorded him. The whole forms a series of unparalleled monographs, including 214 families, 5,134 genera, and 58,975 species.

The Prodromus has been, we may say, the great authority of descriptive botany for half a century. Its order for families has generally been adopted, its form of compilation imitated, and what it proposes or sanctions admitted. It has been of great service in doing away with a number of genera and species for which there was no foundation. As the work was published when most of the new plants were discovered, it contributed greatly to making them known. It includes 657 new genera and 11,790 new species; that is to say, more than Linnæus knew of for the whole vegetable kingdom. M. de Candolle shows, by comparing the volumes three by three from the commencement of the work, that the proportion of new genera in relation to the old constantly dimin ishes, while the proportion of new species remains the same; that is always about 25 per cent. We may, therefore, conclude that by the end of the present century we shall have discovered very nearly all the genera which exist, while with species this is still far from being the

case.

One of the causes of the influence of the Prodromus has been its entire impartiality with respect to the botanists of all countries. The authors have been chosen without reference to nationality. They are thirty-three in number, including MM. Candolle, and of these thirtythree contributors twelve are Swiss, nine French, seven German, three

English, one Italian, one Swedish, one from Holland, and one a Belgian.

Augustin Pyramus de Candolle has written almost a third of the work, 4,303 pages; Alph. de Candolle, 1,387 pages; J. Müller, of Argovie, 1,144; Bentham, 1,133; Meissner, 835; Dunal, 732; the twentynine other assistants, articles less extended. De Candolle, his son, and his grandson (Casimir) have compiled 5,947 pages out of the whole 13,194. The contributors residing at Geneva have furnished six-tenths. The mere correction of proof in such an especial work has been a great labor for the two directors, who have done it all themselves. They have also greatly assisted their colaborers, by taking notes for sixty years, without interruption, of all new descriptions and plates which have appeared in botanical books and journals. These notes, classed by families, form the most complete repertory of descriptive botanical literature ever compiled.

Several motives induced M. de Candolle not to extend the Prodromus beyond the Dicotyledons. The principal one was the great increase in the difficulty of the work, on account of the continually-increasing number of specimens to be examined and of species and characteristics to be determined by the aid of the magnifying-glass. When A. P. de Candolle commenced, an active botanist could describe, according to the custom of the time, 1,500 or 1,800 species a year. Now, with the work prepared as in the last volumes of the Prodromus, and in accordance with the existing state of science, an industrious botanist could describe not more than 300 or 400 species a year. The difficulty of obtaining the manuscripts at the time promised by the authors was another great obstacle. To this cause must be attributed the delay in the publication of the Prodromus, the volumes having appeared more and more slowly in proportion as the number of writers was increased. The execution of this magnificent work has required fifty years, indeed sixty, if we go back to its origin. It has employed three generations of the same family, which is an unusual circumstance in the history of science, and will forever associate the name of Candolle with the most remarkable scientific achievements of Geneva.

WARMING AND VENTILATION.

BY ARTHUR MORIN,

Director of the Conservatory of Arts and Trad 3, Paris.

[Translated for the Smithsonian Institution by Clarence B. Young.]

[Continued from the Smithsonian Report for 1873, p. 318.]

APPLICATIONS.

55. Ventilating by means of common fire places.-Fire-places, though not economical forms of heating-apparatus, produce a very pleasant temperature, and also serve as efficient means of changing the air of occupied apartments.

Natural draught produced simply by the difference between the temperature of the air within the chimney and that without, in many cases, carries off as much as 14,000 cubic feet of air an hour, even when no fire is burning in the fire-place.

With a coal or wood fire of moderate intensity, the amount of air carried. off may be as much as 42,000 cubic feet an hour, or 2,200 cubic feet to each pound of wood burned, and 3,200 cubic feet to each pound of coal burned.

But, with this advantage, common fire-places have the serious defect of drawing in, through the joints of doors and windows, currents of cold air, which run to the fire and chill the backs of those sitting there, an effect which is particularly unpleasant when the face is very much warmed by the fire.

The various forms of apparatus in use, which are designed to warm the apartment, and, at the same time, draw in external air to increase the draft and promote combustion, usually have too small flues, and heat the air to 176°, 2120, or more, which, issuing horizontally at about the height of the occupants of the room, becomes at times unendurable. These forms of apparatus have besides the defect of obstructing the lower portion of the smoke-flue, and of reducing the volume of air casried off. Fire-places made on Douglas Galton's system, with the dimensions given in § 13, do not have these objections, and are unexceptionable means of warming and ventilating during the winter.

56. Use of chimneys for summer-ventilation by means of gas-jets.-Chimneys may easily be made to serve as ventilators during the summer, or on special occasions, by placing in them an iron or copper pipe furnished with several gas-burners. In the chimney of an ordinary apartment,

having an earthen-ware flue 11 inches square and 66 feet high, the amount of air drawn up the chimney to each foot of gas burned will be greater the less gas is burned and the less the temperature in the flue, following pretty nearly the following decreasing series:

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These approximate figures may serve to determine the number of 33 feet burners that will be required to produce any desired rate of change of air in an apartment.

When the chimney is much lower than that just mentioned, it will be necessary to correct the calculated volume of air in the proportion of the square roots of the heights of the flues.

The pipe which conveys the gas to the flue may be easily taken away when not in use, and closed by a blind socket.

This mode of ventilation may be employed to advantage in drawingrooms on reception-days, provided that registers be placed at convenient points for the introduction of moderately warm fresh air.

During the summer, the system of ventilating by means of gas-jets will also allow the room to be maintained at a lower temperature than that of the external air, by drawing in the air from clean cellars to replace that carried off.

Example. The directors' room at the Conservatory of Arts and Trades is ventilated in this way during the summer; and, although the air from the basement is admitted through but a single opening, entirely too small for the purpose, and the doors of the room are constantly being opened, yet the temperature is always 4° lower than the room of the subdirector, which has a precisely similar exposure, but is unventilated, and it is 70 lower than the temperature of the external air in the shade.

57. Auxiliary ventilating-flues.-For unusually large gatherings, in addition to the chimneys, additional flues may be cut in the thickness of the front or party walls, in which gas-jets may be used to produce a strong draught. This method has been tried with success in a house in the Champs Elysées, Paris.

INFANT-ASYLUMS.

58. In these charitable institutions, in addition to securing space and cleanliness, provision should also be made for obtaining an abundant

and regular supply of fresh air, without depending upon the irregular opening of windows.

In this respect, all establishments of this kind, even the model one at the International Exhibition, fall far short. They are warmed by castiron stoves, the imperfections of which were shown in §16.

As an example of what appears proper to be done in such cases,

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five mothers there at a time, while the attendants and patronesses present will usually add ten persons more.

With these data, the maximum volume of air to be carried off and replaced by fresh may reach the following figures, (§ 40:)

For 50 babies, (530 cubic feet each per hour)...

25 visiting mothers, (1,060 cubic feet each per hour).......
10 attendants, (1,060 cubic feet each per hour)....

Total amount of air to be changed every hour.

or 18 cubic feet in a second.

Cubic feet. 26,500

26,500

10, 600

63, 600

This amount greatly exceeds the actual requirement, because the regulations of the asylum forbid the presence of the mothers in the main hall. They are received and nurse their children in a special apartment. The main room is 61 feet long, 24 feet wide, and 15 feet high, having, therefore, a content of about 22,000 cubic feet. With the amount of air mentioned above, the complete change would take place 63600 = 2.8 times an hour, which is quite sufficient to keep the room 22000 in a healthful condition.

in

=

The room is warmed by a hot-air heater, with vertical cast-iron tubes, having altogether about one hundred square feet of heating-surface, communicating with a cold-air duct, which will be described hereafter.

It was intended that this heater should have two chambers: the exterior one, for drying damp linen, carrying the vapor to the chimney; the interior one, opening into the room, for warming dry linen. On account of the expense, these chambers were not made.

There might easily have been placed around the fire-chamber in this heater hot-water pipes connected with a receiver, in order to furnish a supply of water for domestic use.

In summer, the receiver, which, indeed, might have been placed in

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