A NEW TYPE OF SUNDIAL. 693 



methods of counteracting this. The first and simplest is to mount 

 the dial on supports 5>4 ft. to 6 ft. high, so that even the under- 

 side is easily accessible to the eye. The second method is to 

 cement on to the periphery of the dial an inch-wide strip of 

 celluloid roughened like ground-glass. This takes the shadow 

 when it is on the under-side, as in winter, and enables it to be 

 compared with the time-graduations on the upper-side of the 

 dial. The third method which I have found successful" is raJther in- 

 genious, consisting as it does of the use of a small mirror mounted 

 on the south half of the axial wire, parallel to the dial. This 

 makes a northern sun behave as if it were a southern one, casting 

 a spot of light (crossed by the shadow of the wire) on the upper 

 convenient surface of the dial. The mirror is circular, with a 

 central hole to take the wire, and a bored rubber cork cemented 

 on to its back to steady it. It must be capable of motion up and 

 down the wire, being usually 43^ inches from the dial-plate near 

 midwinter, and brought nearer (so as to catch the sun) at the 

 mid-seasons. In summer-time it is not required, and is left in 

 contact with the dial. In plate 26 this mirror is seen partially 

 projecting from behind the top end of the support, and the 

 semicircular spot of light cast by it is round 2 p.m. This spot 

 has the shadow of the wire across it, and the upper edge of this 

 shadow gives the time. The photograph was taken at midwinter, 

 hence the dial is dark. In summer the dial is illuminated and 

 the shadow comes from the centre. The correcting-plate is also 

 opposite 2 p.m., and is fixed to an arm projecting from the 

 stand. The clamp is on the left, concealed by the stand. 

 The holes in the dial are merely to diminish the risk of injury 

 from wind. 



SOME PHOTOGRAPHIC ILLUSTRATIONS OF SOUTH 

 AFRICAN VEGETATION. 



By Iltyd Buller Pole-Evans, M.A., D.Sc, F.L.S. 



{Not printed.) 



Synthesis of Sugars. -Dr. A. J. Ewart, Professor 

 of Botany and Plant Physiology in Melbourne University, has 

 contributed to the Royal Society of Victoria a paper on the 

 synthesis of sugars from formaldehyde, carbon dioxide and 

 water.* The main conditions for a high proportion of sugar 

 are appropriate dilution and a temperature of from 100° C. to 

 110° C. The by-products are formates and methyl alcohol 

 mainly. At low temperatures little or no sugar is produced. The 

 best method is to nm 7 to 8 c.c. of 3 . 5 per cent, sodium hydroxide 

 into 250 c.c. of 0.8 per cent, calcium formate containing 5 c.c. 

 of 40 per cent, formaldehyde while boiling in a condensing flask. 

 The reaction is completed in a few minutes, and as soon as a 

 pale yellowish tinge appears, all the formaldehyde has dis- 

 appeared. 



'■' Proc. Roy. Snc. Jlct.. 31 ( X.S.) [2], 37o-39>7 (191c). 



