20 1 ANNUAL OF SCIENTIFIC DISCOVERY. 



I, do not form a single progression. The relation between their equivalents 

 is, however, exhibited by the scheme a, a + d, a + 2c+cZ/, 2a-\-2d + 2d f , or 

 in numbers, 



Fluorine, .................................... 19 



Chlorine, .................................... 19 + 16-5 = 35'5 



Bromine, .................................... 19 + 33 + 28 = 80 



Iodine, ........................ ............ 38 +33 + 56 = 127. 



Nitrogen, phosphorus, arsenic, antimony and bismuth, form another natural 

 group ; and for their equivalents we have the scheme, a, a + d, a + d-\- d, a + d f 

 , and +cZ+4e^, or in numbers, 



Nitrogen, ................................... 14 



Phosphorus, ................................ 14 + 17 = 31 



Arsenic, .................................... 14 + 17 + 44 = 75 



Antimony, .................................. 14 -j- 17 + 88 = 119 



Bismuth, .................................... 14 + 17 + 176 = 207. 



The author gives similar series for carbon, boron, silicon, and zirconium, a3 

 well as for tin, titanium and tantalum, which we omit. For oxygen, sulphur, 

 selenium and tellurium, Ave have either of the series a, 2a, 5a, 8 f .i, or a, a +</, 

 + 4f7, a -{-Id. Analogy points out the latter as preferable, and we have in 

 numbers, 



Oxygen, .................................... 8 



Sulphur, .................................... 8 + 8 = 16 



Selenium, ................................... 8 + 32 = 40 



Tellurium, .................................. 8 + 56 = 64. 



A common difference of 8 also connects Mg, Ca, Si, Ba, Pb; thus we have 



Magnesium, ................................. 12 



Calcium, ........................ ........... 12 + 8 = 20 



Strontium, .................................. 12 + 32 = 44 



Barium, ..................................... 12 + 56 = 68 



Lead, ...................................... 24 + 80 = 104. 



Lithium, sodium and potassium, belong to a similar series, with a common 

 difference of 16. 



Lithium, .................................... 7 



Sodium, .................................... 7 + 16 = 23 



1'otassium, ................................. 7 + 32 = 39. 



Molybdenum, tungsten, chromium, and vanadium form a similar series, of 

 which the common difference is 22; the progression being 20, 48, 70, 92. 

 The author considers his results as favorable to the idea of Dr. Prout, who 

 supposed the equivalents of all the elements multiples, by a whole number, 

 of that of hydrogen. In the case, however, of chlorine, and perhaps of 

 some other elements, the unit of reference is less than the equivalent of 

 hydrogen, and is probably 0'5. In all the series the first member determines 

 the chemical character of all the other terms. These considerations, the 

 author remarks, will have more weight when he presents the study of a 

 natural family of which hydrogen is the first term, and exhibits the connec- 

 tion between the physical properties of them and the position which each 

 occupies in the series of which it forms a member. 



