452 



SCIENCE. 



[Vol. XIII. No. 332 



The Westinghouse Company at present manufacture five sizes of 

 these dynamos, having capacities ranging from five hundred to 

 five thousand i6-candle-power lights. The machine shown in the 

 cut is the No. 3 dynamo, having a capacity of fifteen hundred 

 h'ghts. 



The field-coils in these machines are supplied vi^ith current from 

 a separate exciter, which is simply a small direct-current machine. 

 The exciter may be driven by an independent engine, or it may, if 

 desired, be attached to the shaft of the dynamo, in which case the 

 dynamo is said to be self-exciting. 



The armature of this dynamo is a structure of great simplicity. 

 The body is of laminated iron plates, freely perforated for venti- 

 lating purposes. A single layer of wire is wound in flat coils back 

 and forth across the face of the armature, parallel with the shaft, 

 being held in place by stops on the ends of the armature. Mica 

 and other insulation is provided, and the whole is wrapped with 

 binding-wire. A ventilator is attached to each end of the arma- 

 ture, drawing a strong current of air through, thus insuring a suffi- 

 cient degree of coolness. These armatures are uniformly wound to 

 deliver a current of a thousand volts, a higher voltage than this for 

 special circuits being obtained when necessary by means of a spe- 

 cial converter. The absence of a commutator will be noticed in 

 the illustration, its place being taken by two plain collecting-rings 

 without breaks of any kind. Narrow collectors rest upon these 

 rings, taking off the current as it is generated. With these collect- 

 ing-rings it is obvious that the adjustment of the collectors is a 

 matter of indifference, as no sparking can occur under any circum- 

 stance, there being no interruption of the current. The matter of 

 dust or more or less oil has no effect, the whole device resolving 

 itself into a detail of great simplicity. 



GEOLOGICAL SURVEY OF NEW JERSEY. 



The work of this survey has been steadily prosecuted during 

 the past year. In the annual report for 1887 it was stated that the 

 Topographic and Magnetic Surveys of the State were completed, 

 and that the reports upon these would be prepared and printed as 

 rapidly as possible. This work is done, and the first volume of the 

 final report of the Geological Survey of New Jersey is being dis- 

 tributed. It is an octavo volume of 450 pages, and contains a re- 

 port on the Geodetic Survey by Professor Edward A. Bowser ; on 

 the Topographic and Magnetic Surveys, by C. C. Vermeule, C.E.; 

 and on the climate of the State, by Professor John C. Smock. It 

 also contains two maps of the State on a scale of five miles to an 

 inch, — one showing its civil divisions ; and the other, its elevations, 

 mountains, ridges, valleys, and plains, together with its rivers and 

 its drainage areas. 



The work now preparing for publication as the second volume of 

 the final report will contain a full catalogue of the minerals found 

 in the State, with their localities ; a catalogue of all the plants 

 growing in the State, with notes of their occurrence and localities ; 

 and also catalogues of its vertebrate and invertebrate animals. 

 Appendices to these catalogues will give some practical and eco- 

 nomic particulars regarding them. Most of the work of preparing 

 these catalogues is already done. 



So much attention has been given in former reports to the study 

 and description of the geological structure of the rocks of the State, 

 that the work still to be done is mainly in combining and syste- 

 matically arranging the materials which have been collected by vari- 

 ous persons who have made New Jersey a study in former years. 

 This is especially the case with the marl and clay formations in the 

 middle of the State, and the limestones, slates, and sandstones in 

 the north and north-western portions. There are some obscure 

 and difficult points of structure in the red sandstone and the gneis- 

 sic rocks ; but it is thought that important progress has been made 

 in clearing up these difficulties, and that the volume on structural 

 geology can be prepared as soon as that above mentioned is out of 

 the way, and that one on the economical geology can then properly 

 complete the series. 



The prompt publication and liberal distribution of the results of 

 the State surveys have continued to meet the approval of the 

 citizens, and to supply suggestive and needed information. The 

 expenses of printing, mailing, and expressage are large ; but the 



returns in the development and wealth of the State abundantly 

 justify the expenditure. The whole system of artesian well-boring 

 was started at the direct suggestion of the survey, and it has 

 brought inestimable sanitary and pecuniary benefits to the whole 

 Atlantic coast, and has been of great service throughout the State. 

 The description of the location and structure of our fire and potters' 

 clays, and its publication, have caused the development of some of 

 the best clay properties in the country, and have made public the 

 immense stores of the best plastic and refractory materials in the 

 immediate vicinity of the great manufactories and markets of the 

 continent. The preparation and publication of the topographic 

 maps, in advance of those of any other State, have tended to draw 

 attention to the peculiar advantages of New Jersey in its location, 

 its varied surface, its healthful seaside and mountain resorts, its 

 water-supply, and its unequalled means of travel and communica- 

 tion. The maps are studied by engineers for projected improve- 

 ments, by citizens seeking homes in the country, by land-owners 

 who desire to improve or open their properties, as well as by in- 

 telligent and inquiring citizens of all kinds who are interested in 

 the development and prosperity of the State. The publication of 

 the condition of the mines, quarries, lime-production, marls, drained 

 lands, water-supplies, and other matters of general interest, is con- 

 tinually inciting to new enterprises and the investment of capital ; 

 and the notes in regard to soils and the means for their improve- 

 ment are helping to develop agriculture, and to greatly increase its 

 products. 



The public supply of pure and wholesome water to the people of 

 the cities, towns, and villages, is of growing importance ; and it 

 needs to be kept before those who should reap the benefits of it. 

 That there are abundant supplies of the best of water to be found in 

 New Jersey, has been pointed out in several of the annual reports. 

 Perhaps that of 1876 contained the most of detail. A bare repeti- 

 tion of some of the points may help to give a more definite idea of 

 the magnitude and importance of the supply, as well as to keep 

 the subject prominently in view. 



From many years' observations it was shown that the annual 

 rainfall varied in different years from about 30 inches in the driest 

 years to about 60 inches in the wettest years, and that the average 

 rainfall in all northern New Jersey was 44ijr inches per year. Ob- 

 servations upon the amount of water to be collected from the 

 Croton watershed show that 60 per cent of the rainfall runs off in 

 the streams. For purposes of safe calculation, however, it was 

 assumed that only 40 per cent of the minimum rainfall should be 

 depended upon : 40 per cent of 30 inches is 12 inches. From a 

 square foot of surface, then, a cubic foot of water can be saved 

 every year, or 7i gallons. From an acre, 326,700 gallons can be 

 collected per year, or nearly 900 gallons per day. From a square 

 mile there can be collected 209,088,000 gallons per year, or daily 

 572,844 gallons. 



The wateished of the Passaic River above Little Falls is 750 

 square miles, being made up of the drainage areas of the following- 

 named streams : Ramapo River, 148 square miles ; Wanoque 

 River, 108 ; Pequanac River, 82 ; Rockaway River, 165 ; Whip- 

 pany River, 59; Passaic River, 188 ; total area of the Passaic and 

 its branches, 750 square miles. Greenwood lake, with a drainage 

 area of 32 square miles, is included in the Wanoque area. Lake 

 Hopatcong, with a drainage area of 27 square miles, naturally 

 found an outlet by the Musconetcong River mto the Delaware ; but, 

 by the dam across its outlet, its surface has been raised so as 

 to find an outlet by the Morris Canal into the watershed of 

 the Passaic. The total area to be drawn from is, then, T]"] 

 square miles. This area can be depended upon to supply 500,000,- 

 000 gallons of water daily. At Little Falls, all this water is in one 

 stream, at an elevation of 158 feet above mean tide ; and it is only 

 16 miles from the centre of Newark, and 22 miles from the centre 

 of Jersey City, or only about half the distance from which the 

 Croton water is carried to New York. By going a few miles 

 farther up the streams, most of the water could be collected at an 

 elevation of 250 feet, or high enough to supply all of those cities by 

 gravity. 



The quality of this water is unquestionable in purity. It is mostly 

 gathered from a country which is mountainous, mostly in forest, 

 and likely to remain so for a long time to come. As a substitute 



