408 . HOBBIES IN DENTISTRY. 



to assert that none such existed, though it has been said that if Mars has 

 moons they are too small to be recognized by any telescope extant; but in 

 any event the probable presence of Martial moons was not to be predicated 

 on any phenomenon exhibited by the planet itself, and if their existence 

 was sus2:)ected it was because it would be more in accordance with the neb- 

 ular hypothesis that they should be present than absent. In a work on 

 astronomy published some forty years ago, we find mention of a phenome- 

 non on Mars which might possibly lead to the idea that the planet was 

 subjected to reflected light from some near body, and that was, that a curious 

 and persistent illumination of the jilanet had been noticed, which, under the 

 circumstances, was unaccountable, save under the hypothesis that the planet 

 was slightly phosphorescent. 



The discover}^ is a triumph both for Professor Hall and for Mr. Alvau 

 Clarke, the maker of the great telescope. It, besides, shows what may be 

 expected of the still more colossal instrument which at no very distant day 

 we hope to see established in the Lick Observatory. — Scientific American. 



HYGIENE. 



HOBBIES IN DENTISTRY. 

 BY A. H. TREGO, D. D. S. 



It is fair to estimate that no comparatively new science has been devel- 

 oped more rapidly than dentistry in the last quarter of a century. It is 

 not surprising, then, where there are so many self-taught and untaught 

 disciples, that there is a field full of "hobbies " and many poor riders. 



One of the most dangerous of these hacknics is the "mallet" for im- 

 pacting gold in cavities of teeth. An endless variety has been introduced, 

 but none that affords general satisfaction. The more skilled and unbiased oper- 

 ators have found the mallet system to be " more or less imperfect and im- 

 practicable, and dangerous in the hands of injudicious operators." One 

 objection is that no mallet has been produced that will strike a " back- 

 action blow." Secondly, it is physically impossible for any " tapper " to 

 know exactly when and how hard to strike; just as it is impossible for one 

 person's muscle to vibrate in unison with another's brain and eye. The 

 danger is that a succession of blows, sufficiently hard to weld gold, is cer- 

 tain to produce congestion of the periodontium. 



Disciples of the mallet claim that " taps " are less painful and injurious 

 than "hand pressure concussion." Patients who have tried both most em- 

 phatically disagree with them, and practice proves that very many teeth 

 are ruined by the use of mallets. To illustrate, one may apply the full 

 strength of the arm in pushing against another's head and not force him 



