TOL. VI.] PHILOSOPHICAL TRANSACTIONS. (5^7 



for the substantiality of light, approach very near to a physico-mathematical 

 evidence, especially with such men as have, either skilfully and carefully made 

 those experiments themselves, or attentively beheld them when made by others. 

 However, he makes a shift to say something by way of answer to all the argu- 

 ments, produced in the first place for the proof of light's being a substance : 

 yet denying, that, though light were an accident, it would follow, that co- 

 lours, called permanent, are something distinct from light, and residing in 

 bodies when light is absent. 



IV. Marci Meibomii de Fabrica Triremium Liber. Amstelodami, 1671, 

 in 4to. 



This discourse treats first of the occasion and original of shipping, and re- 

 lates, that it began with oars, and then was improved by sails, and at last was 

 practised with the use of both. In the beginning, for celerity and fight, they 

 multiplied oars, and for some strength, they fortified their ships with strong 

 beaks, as birds of prey have strong wings and a sharp beak. He ascribes to 

 the Sidonians the first invention of building long ships for war, and the con- 

 trivance of filling them with oars in such a manner, that no void spaces might 

 be left. As broader and shorter ships were built for burthen. 



Galleys he distinguishes into monocrota, wherein one or more rows of men 

 sit in the same level or plain ; and polycrota, in which the rowers sit in divers 

 heights, one above another, as in amphitheatres ; whence the biremis, trire- 

 mis, quadriremis, and so on to the tessaraconteris, the largest that we read of, 

 and recorded to have been made by Philopater. 



In the monocrota he considers the manner of the sitting of the rowers ; and 

 the interscalmium, or the space between the two oars of the same versus or 

 row ; referring the transtra to the polycrota galleys ; where he has occasion to 

 examine the measure of the great and Roman foot and cubit ; as also to give 

 the meaning of the words versus (Gr. qoi-^ot; or ftx,"?) and ordo (Gr. ra^tf.) 



Next he endeavours to explain, in the galleys that are polycrota of 3, -4, 5, 

 or more tiers of rowers, seated in different heights, how those men could be 

 placed. And here he pretends to have been the first that has perfected the 

 way of lessening the height of the ancient galleys, by devising these two ex- 

 pedients ; by the first of which (said to have been published by him 22 years 

 since) he affirms to have showed, so to pla(;e the lateral rowers, as that he that 

 sits behind another, may move his hands and oar under the seat of the rower 

 sitting next before him : by which means three lateral rowers, which, according to 

 Scaliger's way, would require the height of 13-i- feet, will occupy only the space 

 of 74- feet. By the other invention, which he now adds, he pretends to have 

 found a new place in those ships for almost half the number of rowers. 



