10 Meldrum, Development of tJie Atomic TJieory. 



must repel one another. On this line of thought 

 he finds the answer to his own question : — " Why 

 do many salts crystallise nearly neutral in a liquor con- 

 taining a superabundant quantity of acid and \sic'\ of 

 alkali?" Further, on the supposition that particles of 

 water and of acid attract one another, as also particles 

 of water and of alkali, he thought he could account for 

 the water of crystallisation found in many salts, so he 

 explains " why much water doth combine in the crystals 

 of most neutral salts, and why this water of crystallisation 

 separates from the superfluous acid or alkali, and in- 

 troduces little or none of either into the crystals." '' 



In short, on the basis of Newton's theory of a gas, 

 Bryan Higgins taught that chemical combination takes 

 place between acid and alkali in a definite and single 

 proportion. He went little further, if any, with these 

 speculations. His progress must have been greatly 

 hampered by his belief, to which he adhered till about 

 the year 1792, in the phlogiston theory of chemistry, 

 and by his belief in the existence of seven chemical 

 elements, namely, earth, water, air, acid, alkali, phlogiston 

 and light. 



William Higgins (i769?-i825) was trained in chem- 

 istry by his uncle. He assisted Dr. Beddoes in the 

 teaching of chemistry at Oxford (1787), and acted as 

 chemist to the Apothecaries' Hall of Ireland (i 791 -1795), 

 and then to the Royal Dublin Society (1795-1825). He 

 was a Fellow of the Royal Irish Academy and of the 

 Royal Society of London. 



He did not long suffer from the disadvantages of 

 the phlogiston theory, for he was one of the first to 



^^ Biyan Higgins, "A Philosophical essay concerning Light," pp. 201- 

 208, 212-213. 



