184 Scientific Intelligence — Arts. 



19. Dental Parasites. — At a meeting of the American Academy, 

 December 1849, a paper was read by Dr H. J. Bowditch, on the 

 animal and vegetable parasites infesting the teeth, with the effects of 

 different agents in causing their removal and destruction. Micro- 

 scopical examinations had been made of the matter deposited on the 

 teeth and gums of more than forty individuals, selected from all 

 classes of society, in every variety of bodily condition, and in nearly 

 every case animal and vegetable parasites in great numbers had 

 been discovered. Of the animal parasites there were three or four 

 species, and of the vegetable one or two. In fact, the only persons 

 whose mouths were found to be completely free from them cleansed 

 their teeth four times daily, using soap once. One or two of these 

 individuals also passed a thread between the teeth to cleanse them 

 more effectually. In all cases the number of the parasites were 

 greater in proportion to the neglect of cleanliness. 



The effect of the application of various agents was also noticed. 

 Tobacco juice and smoke did not impair their vitality in the least. 

 The same was also true of the chlorine tooth-wash, of pulverized 

 bark, of soda, ammonia, and various other popular detergents. The 

 application of soap, however, appeared to destroy them instantly. 

 We may hence infer that this is the best and most proper specific for 

 cleansing the teeth. In all cases where it has been tried, it receives 

 unqualified commendation. It may also be proper to add, that none 

 but the purest white soap, free from all discolorations, should be used. 

 — American Annual of Scientific Discovery, p. 320. 



ARTS. 



20. The Steamboat New World. — Every year sees some new 

 steamboat constructed, which surpasses in size, magnificence, or 

 speed those previously made. There is no doubt that the me- 

 chanics of this country excel those of any other in their inland 

 steamboato, and it is also probable that in a few years the same 

 can be said of our sea-going steamships, though it must be allowed 

 that those hitherto produced are, with few exceptions, decided fail- 

 ures. During the present year, the new steamboat " New World" 

 has commenced running. She is said to be the longest boat ever 

 put on the stocks in this country, and the longest afloat in the 

 world. Her length is 337 feet ; extreme width, 69 feet ; the 

 engine is 76 feet in cylinder, 15 feet in stroke, and the wheels of 

 iron, 46 feet in diameter. She draws 4^ feet of water. The engine 

 is a low pressure one, and though the boat is so very long she obeys 

 the helm with great readiness. Her decorations are all of the most 

 superb and costly character. 



If we even attain any greater speed either in our inland or sea- 

 going steam-vessels, it will be principally by enlarging their size. 

 Though some improvements will doubtless be made in the engines 



