AUCKLAND INSTITUTE.

New Zealand Herald, Volume XXV, Issue 9180, 9 October 1888, Page 5

AUCKLAND INSTITUTE.

A meeting of the Auckland Institute was held last night at the Museum Buildings, Professor Thomas occupying the chair. The attendanco was rather small, owing to the tempestuous weather. The subject for the evening was a lecture on " Optics," delivered by Dr. Challinor Purchas. In opening, the lecturer stated that as the subject was an exceedingly wide one, he would confine himself chiefly to the optics of the eye. Before doing so, however, he gave a short outline of the chief properties of light, touching on its vibratory nature, and its refraction by passing through glass and other transparent media. The theory of lenses was then briefly dealt with, after which lie described the structure of the human eye, pointing out the various parts on diagrams. Among other interesting topics dealt with was short and long sighteoness, the cause of which was explained, as was also the mechanism by which the eye was focussed on near or distant objects. In connection with this the manner in which .spectacles acted in improving the sight was briefly discussed. The lecture was concluded by a short account of colour-blindness. Professor Brown, who had brought with him the necessary apparatus, displayed the light spectrum on the wall, and the lecturer then stated that there were three distinct types of colour blindness : first, total inability to distinguish any colour ; second, complete blindness for one of the primary colours— red, green, or violet; and lastly, incomplete blindness for all three colours. Red blindness was the most common, and most serious, as it had been the cause of many terrible accidents through inability to distinguish railway and steamer light signals. The subject had been most carefully investigated, and it was found that fully 4 per cent, of mankind were thus affected. At the conclusion of the lecture a cordial vote of thanks was passed to Dr. Purchas, and the chairman expressed regret that the wet eveuing had prevented a larger audience from hearing such an interesting lecture.

The next meeting of the Institute was announced to take place on the 22nd of October.