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 JUTOC 19, 1886.]

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��and PteraphjllumB ; the monocotyledooB throuf;b their Aetbophyllums and Yuccites ; and the Conirerae Ihroiigli their Aibertias, Walchiae, and VoUziaB ; while the less modified ancestral type, which began even In the Permian to as- sume a distinct Salisburian aspect in the genus Ginkgophylium, has cotne down to us, as already described, through the several succes- sive roodificfttions which culminated early in the tertiary in tlie modern form. This general form was somewhat varied, widely distributed, and quite abundant in ntiocene time ; but it is now reduced to a. single species, which was probably restricted to the warmer or more eastern districts of the Chinese empire before it was transferred by human agency, and ac- climnteil in Japan, to which country it is now liopularly credited. But it is said that there is now no part of the world in which it is found in a Strictly wild state, being confined, even in China, to the near vicinity of temples and human habitations.

This interesting tree has for many years been cultivated on the continent of Europe, where it thrives as far north as Copenhagen, but only fruits freely in the more southern districts, notably in the botanic garden at MontpcUier, France, where it has been exhaustively studied Ijy Professor Charlas Martins and the AUrqiiis Sapoila. Id the United States there are now many fine trees ; but they rarely Bower, and, when they do so. the seses are seldom together, so that fnait cannot bo produced. The only ex- ception to this known to me, or to any of whom J have inquired, is the case of a pair of these trees in the grounds adjacent to the University of Kentucky at Frankfort, which are in such close proximity to each other that fertilization regularly tabes place, and fruit is liome.

It is owing to these circumstances that such s|>ecial interest attaches to the coincident flowering this si-oson. for the first time, of the pair of maiden-hair trees in the botanic garden at Washington ; and the rare opportunity, should it be afforded, of witnessing all the stei>8 in the reproductive process of this historic type of vegetable life, will be appreciated by both botanists and vegetable paleontologists.

Lester F. Wabi>.

��THE NEW CROTON AQUEDUCT. Tiic necessity for an addition to the present supply of water of New York has been felt for many years, and the present Croton aque- duct, finished in 1S4'2, has become cntirely inadequale to meet the present requi

��of the city. Never was the need of an addi- tional supply better illustrated than in 1880, when the authorities in chai^ stated, at the end of a prolonged drought, that there was only fifteen days' supply at hand. Timely rains occurred shortly afterwards, and replen- ished the water-sources.

Since 1875, when two projects were pre- sented for an additional water-«upply, numer- ous surveys were made, extending in several instances beyond the limits of the present collecting-grounds ; and in the beginning ol 1883 a committee of citizens, appointed by the mayor at the request of the senate, pre- sented to the legislature a report recommend- ing that provision be made for the ultimate storage of all the water from the Croton basin, and for the immediate construction of a new aqueduct.

This scheme is now being carried out by a commission created by the legislatui'e (May. 1883), and composed of the mayor, comptrol* ler, and commissioner of public works, and of three dtizens at large.

The available watershed of Croton River covers now 338.82 square miles. Its waters are at present collected in several storage- reaervoirs, the lowest of which (Crolon Lake) acts also as a settling-basin, from which the present aqueduct starts, and extends as far as the main distributing reservoir in Central Park. Owing to the limited capacity of the present storage -resen'oirs and of the aqueduct, a vei7 large [iroportiou of the flow of the river is unavoidably wasted over Croton dam.

The present scheme consists in building reservoirs capacious enough to impound the copious spring flows, and in constructing a larger aqueduct, through which the necessaiy allowance of wa ler can be drawn all the year round rri>m the new resen'oirs. It is conse- quently, in a general way, on a larger scale, a duplicate of the present system ; l>ut the very scale on which the work is to be built gives rise (as may be understood from the short description which follows) to many interesting and difllcult engineering problems.

It is estimated, that, in the dryest years, the Croton watershed can furnish a daily supply of 250,000.000 gallons, equivalent to 100 gal- lons per head per day for a population of two million and a half souls, or to 73 gallons per head for a population of three and one-third millions.

In order to store the large amount of water necessary to provide this large daily supply during the dryer months, it has been foimd .idvisable to provide, at first, one reservoir of

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