FRO 



FRU 



827 Frost in England for nine weeks. 

 859 Carriages used on the Adriatic 



Sea. 

 908 Most rivers in England frozen 



two months. 



923 The Thames frozen 13 weeks. 

 987 Frost lasted 120 days : began De- 

 cember 22. 

 998 The Thames frozen five weeks. 



1035 Severe frost on June 24 : the corn 

 and fruits destroyed. 



1063 The Thames frozen fourteen 

 weeks. 



1076 Frost in England from November 

 till April. 



1114 Several wooden bridges carried 

 away by ice. 



1205 Frost in England from January 14, 

 till March 22. 



1407 Frost that lasted 15 weeks. 



1434 From Novem. 24, till Feb. 10, 

 Thames frozen down to Graves- 

 end. 



1683 Frost for thirteen weeks. 



1708-9 Severe frost for many weeks. 



1715 The same for many weeks. 



1739 One for nine weeks : began De- 

 cember 24. 



1742 Severe frost for many weeks. 



1747 Severe frost in Russia. 



1751 Severe one in England. 



1760 The same in Germany. 



1776 The same in England. 



1788 The Thames frozen below bridge ; 

 booths on it. 



1794 Hard frost of many weeks. Ther. 

 at London, mostly at 20 below 

 of Fahrenheit. 



Hoar frost, is the dew frozen or con- 

 gealed early in cold mornings; chiefly in 

 autumn. Though many Cartesians will 

 have it formed of a cloud ; and either 

 congealed in the cloud, and so let fall, or 

 ready to be congealed as soon as it ar- 

 rives at the earth. 



Hoar frost, M. Regius observes, con- 

 sists of an assemblage of little parcels of 

 ice crystals, which are of various figures, 

 according to the different disposition of 

 the vapours, when met and condensed by 

 the cold. 



FROTH spit, or CUCKOW spif, a name 

 given to a white froth, or spume, very 

 common in the spring and first months 

 of the summer, on the stems of certain 

 plants ; it includes and defends the larva 

 /certain species of Cicada, and from the 

 pores of which it is secreted at pleasure. 

 See CICADA. 



FRUCTESCENTIA, in botany, com- 

 prehends the precise tinve, in which, after 

 the fall of the flowers, the fruits arrive at 

 maturity, and disperse their seeds. In 

 general, plants which flower in spring 

 ripen their fruits in summer, as rye ; 

 those which flower in summer have their 

 fruits ripe in autumn, as the vine ; the 

 fruit of autumnal flowers ripen in winter, 

 or the following spring, if kept in a stove 

 or otherwise defended from excessive 

 frosts. The time in which plants ripen 

 their fruit, combined with that in which 

 they germinate and unfold their leaves, 

 gives the entire space or duration of their 

 life, which, in the same species, is pro- 

 portionally short or long, according to 

 the greater or less intensity of heat of the 

 climate in which they are cultivated. In 

 general, it appears, that, if the heat is 

 equal and uninterrupted, the time be- 

 twixt the germinating or sprouting and 

 flowering of annual plants is equal to the 

 interval betwixt their flowering and the 

 maturation of the fruits, or even the total 

 destruction of the whole plant. In very 

 hot climates, an annual plant generally 

 lives as long before as after flowering. 

 But in temperate climates, as France 

 and England, plants which rise in spring, 

 and flower before the month of June, 

 live a little longer before than after 

 flowering ; such as flower in summer, as 

 barley and oats, which flo\ver in June, 

 live as long before as after; while the 

 later plants, which do not rise till au- 

 tumn, live longer after flowering than 

 before. These observations apply chiefly 

 to herbaceous annuals. See Milne's Bo- 

 tanical Dictionary. 



FRUSTUM, in mathematics, a part 

 of some solid body separated from the 

 rest. 



The frustum of a cone is the part that 

 remains, when the top is cut off by a 

 plane parallel to the base ; and is other- 

 wise called a truncated cone. The frus- 

 tum of a pyramid is also what remains, 

 after the top is cut off by a plane parallel 

 to its base. To find the solid content of 

 the frustum of a cone, pyramid, &c. the 

 base being of any figure whatever : add 

 the areas of the two ends and the mean 

 proportional between them together, then 

 one-third of that sum will be the mean 

 area, or the area of an equal prism, of the 

 same altitude with the frustum ; and con- 

 sequently, that mean area multiplied by 

 the height of the frustum will give the so- 

 lid content for the product : 



