80 ANNUAL OF SCIENTIFIC DISCOVERY. 



litres of vapor a minute, I tried to work a small steam en^^inc by 

 solar heat, and my ollorts were crowned with success in June, 

 18G6. In the mean time I liave been able, by very simple appara- 

 tus, to obtain some remarkable effects from insolation, such as 

 the distillation of alcohol, the fusion of sulphur, perfect cooking 

 of meat, bread, etc. None of these experiments, particularly the 

 application of the sun's heat to machinery, have been tried upon 

 a suiliciently large scale. It would, therefore, be useful to repeat 

 them in tro])ical countries, with 'sun-receivers' of suitable di- 

 mensions. We would measure the volume and the tension of 

 steam produced in an hour by a given insolated surface, the pres- 

 sure developed by the sun in a considerable mass of confined air, 

 and the temperature which might be obtained by vast reflectors, 

 formed of a framework of wood covered with plates of silver, 

 etc." 



IMPROVED mariner's COMPASS. 



The Earl of Caithness is the inventor of a new mode of sus- 

 pending ships' compasses, which for efficiency and simplicity is 

 said to surpass anything j-et produced. Instead of the two con- 

 centric brass rings having: their axles at rifi:ht anfrles, known as 

 gimbals. Lord Caithness employs a pendulum and ball, which 

 ball works in a socket in the centre of the bottom of the comi)ass 

 bowl. The compass works, therefore, on one bearing on the ball- 

 and-socket principle, and thus maintains its parallelism with the 

 horizon in the heaviest weather. If we may credit the published 

 reports of the trials, the simplicity of this invention is not more 

 striking than its efficiency. It is stated that it has already stood 

 the most trying tests, and the oscillation of compasses to which it 

 is applied, as compared with the oscillation of the gimbal com- 

 pass, is as degrees to points. 



TO MEASURE HEIGHTS. « 



A veiy compact and useful instrument, called the •' apomecom- 

 eter," that can be carried in the waistcoat-i)ocket, for asom-taining 

 the vertical heights of towers, spires, and other buildings, has been 

 invented in England. It cannot be better explained than i)y quot- 

 ing the description given by ^Ir. Millar, tlie inventor: "The 

 * apomecometcr' is constructed in accordance with the principles 

 which govern the sextant, namely, as the angles of incidence and 

 reflection are always equal, the rays of an object being thrown 

 on the plane of one mirror are from that reflected to the plane of 

 another mirror, thereby making both extremes of the vertical 

 height coincide exactly at the same point on the horizon glass; so 

 that, by measuring the base line, we obtain a result equal to the 

 altitude." 



