144 



The direction and nature of the third counter-work of the Syra- 

 cusans he supposed were also misunderstood by Goelhn, Dr Ar- 

 nold, and other commentators and editors. It did not appear to have 

 been carried in a direction to cut the Athenian lines of circumvalla- 

 tion towards Trogilus, but, after it had reached a certain length in 

 the direction of their wall, it was then carried northwards, and 

 parallel to the Athenian lines ; and this appeared evident from the 

 language employed by the historian, in his description of the battles 

 that were fought between the lines of both parties ; and the use of 

 the preposition Trttg^a. in composition with the verbs oiKo}of<,'ia and 

 i^^of^cti. He also shewed that this parallel wall was afterwards car- 

 ried forward to the lyxa§(r<ov ■retx''^^ ^^ cross wall. The author then 

 described the position of the three Syracusan camps on Epipolse, 

 which were attacked by Demosthenes, in the night expedition to 

 turn the Syracusan lines, and pointed out the errors into which Dr 

 Arnold seems to have falleti, in his account of them, as also the mis- 

 application of the term 7rci^ctriix,icrua, which he thinks should be tt^o- 

 ru'x,'!rux, or an advanced post. He concluded by observing, that 

 the rout of the Athenians must have commenced near the verge 

 of the slope of Epipolse, and not towards the bottom, as has been 

 generally supposed. 



2. Researches on Heat. Second Series. By Professor 

 Forbes. 



The author states, that in a former paper on this subject, having 

 confined himself to the establishment of a number of new facts in 

 the science of heat, embracing its polarization by reflection, refrac- 

 tion, and double refraction, and the depolarizing action of doubly 

 refracting crystals, he proceeded, on resuming the subject, to ascer- 

 tain more accurately the laws of these phenomena. 



Thtijrrst section of the paper relates to the methods of observa- 

 tion employed, and the examination of the values of the degrees of 

 the galvanometer, which, for the most part, do not indicate equal 

 increments of force. Two tables are given. By the first, the sta- 

 tical deviations of the needle are reduced, so as to be measures of 

 the force producing them ; and, by the second, the dynamical ef- 

 fect, or arc moved over by the initial disturbing action, is reduced 

 to the final or statical effect, and thence to the true measure of heat. 

 Several peculiarities attendant <>u the use of the galvanometer are 



kewise discussed. 



