‘* 
Chemistry and Physics. 269 
(na+-nd") being the general formula. With these premises the author 
presets ) compare the equivalents of the elements. The elements F, 
|, Br, I, do not form a single progression, The relation between their 
equivalents is however exhibited by the scheme a, ad, a+2d+d’, 
2a-++-2d-+-2d’, 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 natu- 
ral group, and for their equivalents we have the scheme, a, ad, a+d 
+0’, a+d+2d’, and a--d--4d’, or in numbers, 
itrogen, - 
_ Phosphorus, - - - 144+17=31 
Arsenic, - - - 14--17+44=75 
Antimony, - . - 14417-488=119 
Bismuth, - = = 14-+4-17-+-176=207. 
The author gives similar series for carbon, boron, silicon, and zirconium, 
48 well as for tin, titanium and tantalum, which we omit. 
sulphur, selenium, and tellurium we have either of the series a, 2a, 5a, 
ord, a++-d, a+4d,a+t-7d. Analogy points out the latter as prefera- 
ble, and we have in numbers, 
Oxygen - - - 8 
Sulphur, «ig: bainhd: * port #o BERT 
Selenium, = - - - 8-++32—=40 
Tellurium, - = + 8+4+56=64, 
f common difference of 8 also connects Mg, Ca, Si, Ba, Pb; thus we 
ve 
Magnesium, - -— - 2 
ium, - - - . oi peo 
Strontium, = - - - 124+32= 
arium, - - - 12+56=68 
24-+-80= 104. 
a, Lead, 2, 7 : 
-“Githinm, sodium and potassium belong to a similar series with a common 
difference of 16. 
Lithium, re es eee | 
Sodium, - ee oe - 7+16=23 
Potastinmy, <0 cet a AAS cs 
wilybdenum, tungsten, chromium, and vanadium form a similar series 
ich the common difference is 22, the prog ng Dr. Prout 
ho author considers his results as favorable to the idea of Dr. Prout, 
determines the chemical character of all the other terms. eh, — 
he °ns, the author remarks, will have more weight when he agin 
Study of a natural family of which hydrogen is the first. term, a 
