436 PHILOSOPHICAL TRANSACTIONS. [anNO I678. 



gandis. 2. De Rationum et Fractionum Reductione. 3. De Periodo Juliana. 

 Lond. 1678. 



The first of these three problems, viz. on investigating the distances of 

 comets, it seems, was undertaken at the request of Sir Chr. Wren, and which 

 the author states in this problem, viz. " Four right lines being given in posi- 

 tion in the same plane, to find a fifth, which shall be cut by the four given, so 

 that the interposed segments shall have a given ratio." The solution of which 

 he gives. — ^The second problem shows ingenious methods of reducing ratios and 

 fractions of large terms to other equivalent ones, or nearly so, in much smaller 

 terms, particularly exemplified in the ratio between the diameter and circum- 

 ference of a circle. The third tract teaches how to find what year of the Julian 

 period answers to any given years of these three, viz. the solar and lunar cycles, 

 and the Roman indiction. 



II. Martini Lister e Societate Regia, Lond. Historiae Animalium Angliae tres 

 Tractatus. Unus, de Araneis. Alter, de Cochleis turn Terrestribus, turn 

 Fluviatilibus. Tertius, de Cochleis Marinis. Quibus adjectus est quartus, de 

 Lapidibus ejusdem Insulse ad Cochlearum quandam imaginem figuratis. Lond. 

 1678. 



The first tract contains two books. The former treats of spiders in general. 

 As a description of their several parts, both outward and inward ; of their ge- 

 neration; the nature and emission of their thread; casting their cuticle; of 

 their food; their venom; several either false or dubious traditions concerning 

 them; medicines made of them. — The second book contains a distribution of 

 spiders into their several species, arranged in curious and compendious tables of 

 divisions and subdivisions. He likewise exhibits the figures ; sets down the de- 

 scriptions, place, time of laying, manner of coition. Describes their eggs, 

 nests, nets, threads. Speaks of their food and manner of living; their very 

 high ascent into the air, &c. 



The second tract has three parts. The first of snails in general. As, of 

 their shells, and other parts both outward and inward; their saliva, eggs, food; 

 use in medicine ; diet, &c. — The second of land snails. — The third of river 

 snails. The several sorts being figured, described, and comprised by the author 

 in tables of subdivisions. 



The third tract is of sea snails, which by the author are figured and distri- 

 buted into tables, like the former. 



The last book, de Cochlitis Angliae, presents the figures and descriptions of 

 many of this kind, classed in tables like the others. 



The author is rather of opinion that these figured bodies are not petrified 

 shells, but bred in the earth, like other stones. 



