IHAP.LKKKTS 



DIAL AND DIALLING 



ful in drla\ in- the progress of the disease. Flannel 

 sin. ul. I !> \\,>in in-\t the skin, iiinl tin- languid 

 function of tin- cutaneous perspiration aided by tin- 

 warm liutli, ''specially, perhaps, tin- vupinir bath 

 e.g. that fin-iii known tin tin- Kit-Maii Iciili. The 

 Turkish liath, which attract* a large quantity of 

 water through the skin, is leas suitable to s'uch 



CiUscs. 



DiaulcretS & remarkable mountain of the 

 Bernese Alps, Switzerland, mi the frontiers of iJ.-m 

 anil Viilais, \\itlt a height of IO.IM! feet uliove tin- 

 sea. Tlie IMableiets, with their four main jK'iiks, 

 are composed of limestone strata, the lower l>eds of 

 which are so soft and shaly that they are easily 

 disintegrated, and masses falling down into the 

 valley from above cause the most terrible catas- 

 trophes, as in 1714 and 1749. 



Diacaustic. See CAUSTICS. 



Diachylon. See PLASTER. 



Diadochi. See GREECE, Vol. V. p. 388. 



Disi'resis (Gr., from diaireo, ' I divide' ), a term 

 used in Grammar to signify the resolution of a 

 diphthong, or of a contracted syllable, into two 

 syllables; as Lat. aura: into aiinn. The name is 

 also given to the mark " placed alx>ve a vowel 

 letter to indicate that it is to ! independently 

 pronounced, and not in conjunction with a pre- 

 ceding vowel ; as in the above example, or in the 

 word aerial. See UMLXuT. 



Diagnosis (Gr., from dia, 'through,' and gndsis, 

 'knowledge'), in Medicine, the discrimination of 

 diseases. It includes the study of all the vital 

 phenomena of diseases, and also of their appear- 

 ances after death, in so far as this can aid their 

 discovery during the life of the patient. It is usual 

 to speak of rational or physiological diagnosis, or 

 diagnosis by symptoms i.e. changes chiefly func- 

 tional, observed by the patient ; and of physical 

 diagnosis, or diagnosis by signs i.e. objective 

 phenomena appreciable by the senses of the 

 observer. The latter method of diagnosis h.-i- 

 been much enlarged in scope and increased in 

 importance by the modern methods in medicine of 

 Auscultation (q.v.) and Percussion (q.v.), and also 

 by the great advances made in physiological chem- 

 istry, and by the use of the microscope. Skill in 

 diagnosis is one of the highest gifts of the phy>i 

 .-i.iii. and nothing distinguishes the man of long 

 experience from the tyro more than this unerring 

 insight into some unseen disease. See STKTHO- 

 sn (no, LARYNGOSCOPE, OPHTHALMOSCOPE, &c. 



Diagonal Scale* See SCALES (M.\rin.M\ 



TICAL ). 



Dia'goras (surnamed the 'atheist'), a Greek 

 poet and philosopher, was born in Melos, an island 

 of the Cyclades. He is said to have been a disciple 

 of Democritus of Abdera, and he is alluded to l>y 

 Aristophanes in the Clouds ( 424 H.c. ). He seems 

 to have been witty and fearless, and probably 

 treated the superstitions of the popular religion 

 with contempt. He was formally accused of im- 

 piety in 411, and only saved his life by flight to 

 Pallene, and afterwards to Corinth, when- he died. 

 He wrote lyrics and a philosophical work, none of 

 which have been preserved. 



Dial and Dialling. A sun-dinl is an instru- 

 ment for measuring time by means of the motion of 

 the sun's shadow cast by a stile erected on its sur- 

 face. It is an instrument of very great antiquity, 

 and before clocks and watches liecame common, it 

 was in general use as a time-keejK-r. Some old 

 sun-dials are very elaltorate e.g. that at Glamis 

 Castle, Forfarshire ; and many lear quaint mottoes 

 (cf. I.fixnre Hour, 1870, p. 413; and Mrs Catty's 

 Book of Sun-Dials, new ed. 1889). Dial-making was 

 154 



then un i in pin taut brunch of mathematical *t' 

 now it i* more an oliject of ciiu'u\ th.ui utility. 

 A dial consists of two part* tin- MM or gnomon, 

 usually the edge of u plat*- of nn-t.il. alu.i\- madr 

 parallel to tin- earth's axi*, and (Hunting toward* 

 tin- north pole; and tin- ,l,nl /,t>m- . whirli nui\ !- 

 of any hard sulmtance, and on which are marked 

 the directions of tin- shadow for the several hour* 

 ol the day, their halved, quarter*. \i . l>ial- i- 

 various names, accord ing m-.-ily to tin- ponitionji 

 which they are constructed to iM-cupv. \Vln-n tin- 

 dial plane is on the plane of tin- hori/on, tin- dial is 

 called a horizontal dial ; when |er|>endicular to that 

 plane, a vertical dial. An qMinoctial dial i* one 

 whose plane is parallel to tin equinoctial plain-. 

 The south dial, north dial, eaM dial, west dial, jiolar 

 dial, declining dial, are named from the portion 

 of the dial-plane. The cylindrical dial b a dial 

 drawn on the curved surface of a cylinder. The 

 ring dial is an ingenious small portable dial, but 

 rather a curious toy than a philosophical in*tm 

 ment. A night or nocturnal dial is an instrument 

 for showing the hour of the night by the shadow of 

 the moon or stars. Moon-dials may be constructed 

 relative to the moon's motion ; or the hour may be 

 found by the moon's shadow on a sun-dial. Kut 

 liecause of the irregularity of the moon's motion, 

 due to its varying speed at different parts of its 

 orbit, the time so found is subject to considerable 

 error. 



Dialling. The stile of a dial being parallej to 

 the earths axis, those familiar with spherical trigo- 

 nometry will readily see that the problem of con- 

 structing a dial resolves itself into that of ascer- 

 taining where the hour-lines cut a given circle, with 

 a view to the graduation of the dial-plane. Suppose 

 Pep (Kg. 1 ), a hollow and transparent sphere, as 

 of glass, to represent the earth ; and suppose its 

 equator divided into 24 equal |>arto by the meri- 

 dians a, b, c, if. &c., one of them pacing through a 

 given place, say London (see HORIZON), at the 

 point a. If the hour of twelve be marked at the 

 equator, t>oth on the latter meridian and that 

 opposite it, and all the rest of the hours in order on 



Fig.1. 



the other meridians, thone meridian* will he the 

 hour-circles of London. U"cause, a the sun appears 

 to move round the earth in 24 hours, ho will IMUW 

 from one meridian to another in one hour. Tnen. 

 if the sphere has an opaque axis, a* Pqp, terminat- 

 ing in the Junes P and ;, the shadow of thi* axis 

 would fall, in ihe oour-e of the day, on every par- 

 ticular meridian and hour, as the sun came to the 

 plane of the opposite meridian, and would thus 

 show the time at London, and at all other places 



