222 THE MINOR PLANET MT I9II. 



191 1, it approached the Earth with 0.203 °f the mean distance of 

 the Sun. As the planet was in perihelion at the end of August 

 and opposition took place in October, it is evident that, although 

 the opposition was a favourable one, it was not the most favour- 

 able which can occur. Its period is 4.157 years, so that every 29 

 years it and the Earth come into the same relative position. 



SIR DAVID GILL. — It is announced in a recent number 

 of Science that Sir David Gill has been elected the first honorary 

 member of the Astronomical and Astrophysical Society of 

 America. 



Irrigation by Sun-power in North Africa. 



— Details have recently been given of a pumping plant on the 

 banks of the Nile in which the direct rays of the sun constitute 

 the motive power. Five parabolic reflectors are mounted on steel 

 frames 204 feet long, 20 feet apart, and having an area of 13,500 

 square feet. These reflectors are kept in a constant position rela- 

 tive to the sun by a thermostat. The solar rays are concentrated 

 on a central boiler so as to raise steam at 100 lb. pressure, driving 

 pumps delivering 6.000 gallons per minute with a 30 feet lift. 

 The initial cost of the plant is £4.000. and the annual expenses 

 £750. A steam plant of equal power would cost £2,000, with 

 annual charges of £550, excluding fuel. 



A Percentage Compass Dial. — Mr, J. G. Fergus- 

 son's percentage unit of angular measurement is claimed to pro- 

 vide an easy method of finding the ratio between base and hypote- 

 nuse, or between base and perpendicular, and to effect an immense 

 saving in all angular computations as well as a considerable sim- 

 plification of field calculations. Mr. Fergusson has made a 

 oractical application of his system to the magnetic compass dial, 

 whereby the latter is declared to be converted into a simple and 

 accurate range finder. The compass dial proper has an outer 

 circle divided in percentages, and an inner circle divided in 

 degrees, so that the compass may be read at a glance in both per- 

 centage units and degree units. Surrounding the floating com- 

 pass card, and independent of it. is a circular scale of Natural 

 percentage cosines, for the purpose of facilitating calculations. 

 By the aid of this outer circle it is asserted that any problem in 

 plane trigonometry may be solved by simple arithmetic. Amongst 

 other advantages claimed for this compass card it is stated that 

 the calculations of navigators, surveyors, and travellers may 

 thereby be reduced to a minimum, and they are enabled to find 

 at once, as they go along, (1) the difference of latitude and 

 departure, (2) the closure angle of a compound traverse, and (3) 

 the length of the closure line. The compass card is procurable, 

 either mounted or unmounted, from Messrs. Longmans, Green & 

 Co., London. 



