350 Professor De Morgan on the 
Sulphate of ironand ammonia . . 6HO 2°27 
Sulphate of iron and potash . . . eae 2°47 
Sulphate of zinc and potash . . . sae 2°60 
Sulphate of copper and ammonia . ie 2°63 
Sulphate of zinc and ammonia... oe 2°73 
Sulphate of copper and potash . . ves 3°04 
Sulphateiobsqday., i. ais) bosnart o0hOd. Oy aap 
Sulphate of potash . . . . . . anhydrous 1°51 
Sulphate ofammonia . . .. . vila 0°51 
Chromate of potash. . . .. . wax 1°18 
Bichromate of potash . . .. . ‘ay 3°96 
Nurate of potash’ ii;)s sso, sa vents ene 3°96 
Terchromate of potash . ae: ate oy 
Biphosphate of potash . . . . . 2HO = 2°24 
Binarseniate of potash . tae ode 
Sulphate of water and potash. . . anhydrous 1°95 
2. Heat disengaged in the complete hydration of anhydrous 
salts. 
Sulphate of magnesia. . . . . 5°25 
Sulphate tof Zine! 1s Ne eatine teh KOuee 
Sulphate of copper . . . . . 4°°40 
Sulphate of manganese . arr 
Sulphate of magnesia and potash . 3°90 
Sulphate of zinc and potash . . 4°30 
Sulphate of copper and potash . 5°01 
3. Heat disengaged by the combination of the first atom of 
water in the magnesian sulphates. 
Sulphate of water. . 2. . . . 1%47 
Sulphate of copper . . . «© . 1°47 
Sulphate of manganese . . . . 1°43 
Sulphate of magnesia . . . . 1°30 
Sulphate of zinc ‘i> heidghen musket Sa 
Simple relations are observed between the quantities of heat 
disengaged by the sulphates of magnesia and zinc, which ap- 
pear to belong to one class, while the sulphates of water, cop- 
per and manganese belong to another class. 
LVIII. On the Invention of the Circular Parts. 
By Professor Dr Morean. 
To the Editors of the Philosophical Magazine and Journal. 
GENTLEMEN, 
THE object of this communication is to point out that a 
very material portion of Napier’s “rule of circular parts ” 
was published by Torporley twelve years before it was pub- 
