Prof. H. Hennessy on Ronayne's Cubes, 183 



where s is the heat-capacity in electric units (water =4*49). 

 For a certain allowable gain in temperature per unit time 

 and a given mass, that material is the best which has the 

 greatest specific heat. A metal of low atomic weight would 

 therefore have the preference. If the volume of the sub- 

 stance be taken as fixed, we must make the product of 

 density and specific heat as great as possible. This product 

 is highest for iron and steel (*90), then follows copper ('80), 

 platinum (*72) ; and gold (62). There would be an appre- 

 ciable advantage in substituting a steel wire for a platinum 

 one, if small differences of temperature are to be detected by a 

 change of resistance, especially as the temperature-coefficient 

 of electric conductivity is considerably higher than that of the 

 other metals. There are, however, obvious disadvantages 

 connected with the use of steel which in most cases w r ould 

 counterbalance its greater sensibility. 



XVIII. Ronayne's Cubes. 

 By Professor H. Hennessy, F.B.S.* 



A FEW years since I was presented by Mr. S. Yeates 

 with a pair of equal cubes, one of which could pass 

 obliquely through the other. These objects had been for a 

 long time in his father's possession, but there was no record 

 as to where or by whom they were made. At first I paid 

 little attention to the cubes, as I looked upon them merely 

 as mathematical curiosities. Not long since, on perusing 

 Gibson's ' History of Cork/ I came on a passage extracted 

 from Smith's ' History of Cork,' published in 1750, in which 

 a pair of interpenetrating cubes is distinctly referred to as 

 the invention of Mr. Phillip Ronayne, of the Great Island 

 near Cove (now Queenstown). The cubes were said to be 

 constructed after Mr. Ronayne's design by Mr. Daniel Voster, 

 who was at this time teacher of mathematics in Cork, and 

 editor of the well-known book on Arithmetic, compiled during 

 the early part of the last century by his father, Elias Vosterf . 



* Communicated by the Author. 



f Passage in Smith's ' History of Cork ' : — 



" Not far from the castle of Belvelly is Ronayne's Grove formerly 

 called Hodnets Wood ; [now Marino] a good house and handsome im- 

 provements of Philip Ronayne, Esquire. From the gardens one has a 

 charming view of the river and shipping up to Cork, as also the town of 

 Passage on the opposite shore. This gentleman has distinguished himself 

 by several essays in the most sublime parts of mathematics ; among 

 others by a treatise on Algebra, which has passed through several editions, 

 and is much read and esteemed by all the philomaths of the present 

 time. He has invented a cube which is perforated in such a manner 



