THE MOST POWERFUL TELESCOPE. 



337 



duce any of them by any process analogous to that employed for vac- 

 cination. 



All these reports and facts relate to vaccinations performed with 

 humanized lymph, and previous to 1876. The most careful examina- 

 tion of every reported or suspected case among the 120,000 vaccina- 

 tions performed up to that time failed to furnish a single case of the 

 transmission of disease of any kind whatsoever from one person to 

 another by means of vaccination. 



In order, however, to avoid as far as possible the prejudice which 

 was at one time so widespread in this matter, no humanized lymph 

 has been used by the Vaccinating Corps for nearly three years. All 

 the virus now used is eighth-day lymph taken from healthy calves 

 carefully selected and kept in the country under the supervision of the 

 inspector, exclusively for this purpose. 



No very special advantage is claimed at present for this over prop- 

 erly selected humanized lymph ; if, however, any difference is ob- 

 servable in the results, it is in favor of the bovine lymph, as affording 

 fewer cases of troublesome inflammation. 



One advantage is decided : it has tended to diminish a prejudice, 

 and so remove in some degree an objection to vaccination. 



It is in the face of an abundance of facts such as these, instead of 

 the badly observed and badly studied facts of fifteen years ago, that 

 intelligent people now must doubt the safety and utility of vaccination. 



THE MOST POWEEFUL TELESCOPE IN EXISTENCE. 



By E. NEISON, F. K. A. S. 



WHICH is the most powerful telescope in existence ? Define the 

 meaning which ought to be attached to the adjective " power- 

 ful " in this question. The most powerful telescope in existence is 

 that existing telescope which can do the most work. The work of a 

 telescope may be said to be to enable you to see and to enable you to 

 measure. Therefore, that telescope with which you can see most and 

 can measure best is that which can do the most work, and is unques- 

 tionably the most powerful telescope in existence. 



Which is the most powerful telescope in existence ? 



Every one has heard of the two giant telescopes which were con- 

 structed nearly forty years ago by the late Lord Rosse, and which 

 were erected at his residence at Parsonstown, about fifty miles from 

 Dublin. The first great telescope constructed by Lord Rosse was a 

 reflecting telescope with a speculum three feet in diameter and twenty- 

 six feet in focal length. It was carried in a ponderous tube moving 

 in a massive iron mounting by means of ingenious machinery. When 



TOL. XTI. — 22 



