119 



His Grace the Archbishop of Dublin mentioned the fact 

 that tar was found to be an effectual preservative against the 

 Potatoe disease, provided the potatoes intended for seed be 

 previously dipped in tar slightly warmed. 



The Rev. Dr. Robinson gave an account of the present 

 condition of the Earl of Rosse's great telescope, and detailed 

 some observations made with it during a recent visit to Par- 

 sonstown. 



In 1845 he had laid before the Academy the results ob- 

 tained by Sir James South and himself, at the first trials of 

 that magnificent instrument. The most remarkable of them 

 had reference to what has been called the Nebular Hypothe- 

 sis, in which it is supposed that nebulous matter forms suns 

 and planets by its gradual condensation. Above fifty nebulae, 

 selected from Sir John Herschel's catalogue, without any limi- 

 tation of choice but their brightness, were all resolved ivithoiU 

 exception. From this he conceives himself authorized to ask, 

 is there any evidence that nebulous matter has real exist- 

 ence? 



The appearances which were supposed to indicate the gra- 

 dual condensation of this imaginary fluid, namely, an increase 

 of brightness towards the centre (sometimes almost looking 

 like a star surrounded by a faint atmosphere), were shown to 

 be caused by a peculiar construction of the systems in which 

 they had been found. This the telescope demonstrated to con- 

 sist of a central cluster, mostly globular, of comparatively 

 large stars, surrounded by an exterior mass of much smaller 

 and fainter stars, whose arrangement is often circular and thin 

 like a disc. When seen obliquely, they seem like long oval or 

 pointed rays ; and in this case, from the optical condensation 

 of their component stellar points, the resolution is more diffi- 

 cult, but even here it was invariably effected. 



He has often been asked why this instrument had given 

 no further results. They who put the question had but a 



