

DIP 



and pistils are in separate flowers, and on 

 separate plants. 



DIOPHA'NTINE PROBLEMS. A 

 species of problems, in which it is re- 

 quired to solve certain questions, the an- 

 swers to which shall be whole numbers 

 only. They are found in a treatise on 

 Algebra by Diophantus, an Alexandrian 

 Greek, who lived in the second or third 

 century of the present era. In character 

 they closely resemble the Hindoo Algebra. 



DIO'PSIDE (3<o>//<f, a view through). 

 A mineral which may be considered as 

 the type of the augite genus. Several 

 varieties, differing little from the above, 

 are called baikalite and fassaite, names 

 indicative of their locality. 



DIO'PTASE. Emerald copper ore ; a 

 crystallized silicate of copper, found in 

 Siberia and the Bannat. 



DIO'PTRICS (^t'oTTTpa, an optical in- 

 strument). That branch of the science 

 of Optics, which treats of the refraction 

 of light, when it passes through different 

 media, as air, water, glass, &c. Tlie phe- 

 nomena are generally referred to the sub- 

 ject of refraction. 



DIO'SMEiE. The Buchu tribe of 

 Dicotyledonous plants. Trees and shrubs 

 with leaves exstipulate, dotted ; flowers 

 axillary or terminal, polypetalous, her- 

 maphrodite ; stamens hypogynous ; ova- 

 rium many-celled ; fruit consisting of 

 several concrete capsules ; seeds twin or 

 solitary, 



DIO'XIDE. According to the electro- 

 chemical theory, the elements of a com- 

 pound may, in relation to each other, be 

 considered oppositely electric ; the equi- 

 valents of the negative element may then 

 be distinguished by Latin numerals, those 

 of the positive by Greek ; thus a biji- 

 oxide denotes a compound which con- 

 tains two equivalents of the negative 

 element oxygen ; whereas a d/-oxide in- 

 dicates that one equivalent of oxygen is 

 combined with two of some positive body. 

 And so of 6i-chloride, di-chloride, &c. 



DIP. When a geological stratum does 

 not lie horizontally, but is inclintd, it is 

 said to dip towards some point of the 

 compass, and the angle it makes with 

 the horizon is called the angle of dip or 

 inclination. 



DIP OF MAGNETIC NEEDLE. The 

 angle which the magnetic needle, when 

 poised so as to move freely in a vertical 

 direction, makes with the plane of the 

 horizon. It is more scientifically termed 

 the inclination of the needle, or the mag- 

 netic inclination. 

 109 



DIP 



DIP OF SEA HORIZON. The ap- 

 parent angular depression of the visible 

 horizon, caused by the position of the 

 observer above the surface of the sea. 



DI'PHYDA (air, twice, ^uw, to grow). 

 A group of the Acalephce, named from 

 the genus diphyes, in which each animal 

 seems to consist of two portions so 

 slightly joined together, that it is diffi- 

 cult to understand their connexion. 



DI'PLOE' (3i7r\6n, a joining). A term 

 applied by Link to the parenchymatous 

 substance of the leaf, which lies imme- 

 diately beneath the two surfaces. See 

 Mesophyllum. 



DI'PLO-GANGLIA'TA {b^irXow, dou- 

 ble, '^af'iKiov, a nerve-knot). A desig- 

 nation of the Entomoida, or articulate 

 animals, which have *' their nervous 

 columns arranged in the same relative 

 position as the diplo-neura, with the gan- 

 glia increased in size, and corresponding 

 with the increased development of the 

 segments and of their lateral appen- 

 dages." — Grant. 



DI'PLO-NEURA {dmXovf, double, 

 vevpov, a nerve). A designation of the 

 Helminihoida, comprising the various 

 forms of Worms, in which the nervous 

 columns have their ganglionic enlarge- 

 ments very slightly developed, and are 

 marked by a greater lateral separation 

 from each other along tUe median line, 

 than is observed in the next sub-king- 

 dom." — Grant. 



DIPLO'PTERA (3<7rXou9, double, me- 

 p6v, a wing). A group of aculeate hy- 

 menopterous insects, which have their 

 upper wings folded longitudinally, when 

 at rest, as in some species of wasp. 



DIPLOTE'GIA (dtTTAoDc, double, -re- 

 yof, a covering). In Botany, a compound 

 fruit, differing from the capsule only in 

 being adherent to the calyx. It occurs 

 in campanula. 



DIPNEUMO'NEiE (3k, twice, wi/ew- 

 jjLUiVy a lung). A section of spiders which 

 have only two pulmonary sacs. 



DIPPEL'S OIL. An animal oil pro- 

 cured by the destructive distillation of 

 animal matter, especially of albuminous 

 and gelatinous substances. 



DI'PTERA (dif, twice, Trrepov, a 

 wing). An order of insects which have 

 only one pair of wings fully developed, 

 and these are on the mesothorax. Instead 

 of posterior wings, there are pedunculated 

 appendages, called halteres or poisers. 

 The mouth contains a soft proboscis, of 

 which the common house-fly affords a 

 familiar instance. See Rhipiptera. 



