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THE STANDARD DICTIONARY OF FACTS 



white robe, with a black gaberdine, and a 

 pointed black cap. 



Drawing. The art of representing on a 

 flat surface the forms of objects, and their posi- 

 tions and relations to each other, was prehistoric 

 in origin. 



Drawings may be divided into five da -MS: 

 sketches, finished drawings; studies, academic 

 drawings, and cartoons. First sketehes are the 

 ideas put on paper by an artist, with the inten- 

 tion of carrying them out with more complete- 

 :id detail in some more elaborate work. 

 They are merely intended to fix and retain his 

 fir.-t thoughts. Finished drawings are such as 

 :vt';;llv executed and made complete in 

 all their parts. By studies are generally under- 

 stood separate parts of objects carefully drawn 

 either from life or from figures in relief ; for ex-' 

 ample, heads, hands, feet, arms; but sometimes 

 the term is applied to drawings of entire figures.. 

 To this class also belong drawings of the skeleton 

 and muscles, as well as of draperies, animals. 

 trees, foregrounds, or other parts of landscapes. 

 Academic drawings are those made in art acade- 

 mies from a living model in lamplight which 

 brings out the shadows more than daylight. 

 The position of the model is carefully arranged 

 at the commencement of each sitting, and in that 

 position he is required to remain. In this way 

 the learners practice the drawing of the figure in 

 various attitudes. In studying drapery and 

 dress, a lay figure, made of wood and with mov- 

 able joints, is clothed in various styles, and 

 drawings made from it. Cartoons are drawings 

 made on stout paper of the size of the painting 

 to be executed from them. They are mostly 

 employed for pictures of large size, and are regu- 

 larly used by fresco painters. The design is 

 pricked through or traced from the cartoon on 

 the surface that receives the finished picture. 



Dream. A series of mental impressions 

 occurring to sleeping persons, and which, there- 

 fore, are not under the command of reason. 

 Dreams have been referred to various causes; 

 among others, to direct impressions on the or- 

 gans of sense during sleep; to the absence of a 

 power to test the inaccurate conclusions drawn 

 from one set of impressions by other impressions ; 

 to a disordered state of the digestive organs ; to 

 a less restrained action of the mental faculties; 

 to the suspension of volition while the powers of 

 sensation continue, etc. In health there is a less 

 tendency to dream than in disease ; in the earlier 

 than in the later periods of life; and the very 

 act of dreaming shows that the brain is not en- 

 joying a complete state of rest. The phenomena 

 of dreams are yet too little studied to enable us 

 to attest much with certainty regarding them. 

 The popular belief has frequently ascribed them 

 to supernatural agency, especially where there 

 has been any coincidence between a dream and 

 an external event; and it may be said that if 

 many of the instances of remarkable dreams 

 may be explained by natural causes, there are 

 others so well authenticated that we cannot al- 

 together discredit them, that are manifestly 

 unexplained by any natural means. 



Dynamics. That branch of the science 

 which treats of the action of force in producing 

 motion. It treats of bodies not in equilibrium, 



as static* treats of bodies at rest. Dynamics is 

 divided into two parts kinematics.' which in- 

 vestigates the circumstances of mere motion 

 without reference to the bodies moved, the forces 

 producing the motion, or to the forces called into 

 action by the motion; and kinetic*, which in- 

 vestigates the nature and relation of the forces 

 which produce motion. Dynamics has to do 

 with the primary conceptions of space, matter. 

 time, and velocity, each of which admits of 

 numerical estimation by comparison with units 

 arbitarily chosen; hence dynamics is a science 

 of numbers. It is usual to consider the subject 

 in two parts: the dynamics of a particle, and the 

 dynamics of a rigid' body. The science owes its 

 origin to Galileo, to whom is due the law of the 

 acceleration of falling bodies. Huyghens added 

 the theories of the pendulum and centrifugal 

 force, and Newton developed the science, and 

 applied it to the infinitesimal calculus. 



Electricity, from the Greek elektron 

 (amber), the name applied originally to the un- 

 known cause of the attractions, repulsions, spark- 

 lings, etc., which attend the friction of amber 

 and similar substances. The same cause is now 

 recognized as giving rise, under various circum- 

 stances, to many phenomena. Many attempts 

 have been made to ascertain the true nature of 

 electricity, but it cannot be said that we have 

 yet any sure knowledge of what this subtle agent 

 really is. Electricity behaves as if it were an 

 incompressible fluid substance, but it differs 

 from all known fluids in so many particulars 

 that it may be asserted that whatever else it 

 may be, it is not a fluid in the ordinary sense of 

 the* word. Neither is it a form of energy, though 

 electrification as distinguished from electricity 

 certainly is such. Many scientific men hold the 

 view that electricity is the ether itself (the elastic. 

 incompressible medium pervading all space and 

 conveying luminous and other vibrations), and 

 that the phenomena of positive and negative 

 electrifications are due to displacement of the 

 ether at the surfaces of bodies. The researches 

 | of Hertz, who, by direct experiment, verified 

 'James Clerk Maxwell's brilliant theory that 

 electrical action is propagated through space 

 by wave motion in the ether, differing only in 

 respect of wave length and period from the 

 vibrations which constitute light, have been 

 of the unmost value in helping to arrive at a 

 solution of this question. Investigations into 

 the phenomena of electric discharges in high 

 vacua, followed by the discovery of Roentgen 

 of the X-Rays, have also thrown great light on 

 the subject. The applications of electricity are 

 extremely varied. Its employment for teleg- 

 I raphy and electro-metallurgy, for chemical and 

 for medical and physiological purposes, for the 

 1 production of light to illuminate streets and 

 buildings, for driving vehicles and machinery 

 of various kinds, may be mentioned as examples. 

 Motor. For practical purposes, to produce 

 continuous power, it is most convenient to use 

 a machine called a motor, which is so arranged 

 that the electricity traverses a wire wound (in 

 the form of one or more coils) many times around 

 a suitably-shaped frame of iron called a field 

 I magnet or simply a field. The current so circu 

 I lating round the field magnetizes, or as it is 



