Dr. Thoinas AndreiuH : The Great Chemist 113 



He repeats his question as to the chemical distinction between 

 Trapp and other rocks, making the interesting point, that, for 

 want of such a criterion he finds Playfair and Allan placing the 

 Portrush Ammonites as being found in Siliceous slates while 

 Dr. Richardson and hundreds of others called it Siliceous Trapp 

 or Basalt. He gives him numerous commissions to haunt the 

 bookstalls looking for volumes which are wanting in certain series 

 in the Doctor's library, and we form an idea of the amazing 

 variety of the literary and scientific interests of McDonnell. 

 He finishes by discoursing upon the effect of altitude on the heart 

 and the rate of respiration and urges Andrews if ever he should 

 gain access to Gay Lussac, to ask him to describe his sensations 

 during his famous balloon ascent of 22,000 feet. I cannot take 

 time to quote further from this most interesting correspondence, 

 but we must wonder greatly when we think it is addressed to a 

 boy wanting some months of seventeen. 



After his arrival in Paris Andrews presented his letters, and 

 was very kindly received by some of the great scientists then in 

 the city. It was vacation time and none of the regular schools 

 were open, but he entered some classes specially intended for 

 students remaining in Paris at such a season, and congratulated 

 himself that he was using h?s time to so much advantage. He 

 ultimately succeeded in gaining admission to the laboratory of 

 M. Dumas, and ever after retained the friendship of this great 

 man. Unfortunately a severe illness compelled him to leave 

 France earlier than he had intended, and on his return to Ireland 

 he entered Dublin as a medical student. While there he con- 

 tinued his great interest in Chemistry and laboured diligently in 

 his preparation for his profession. During his student days he 

 published a remarkable paper on the " Chemical Changes in the 

 blood of Cholera patients," gaining his material during the great 

 epidemic which broke over Belfast in 1832. He completed his 

 medical course in Edinburgh where he took his degree, obtaining 

 the diploma of the Royal College of Surgeons in April, 1835, and 

 his M.D. in the August of the same year. It was immediately 



