54 Mr. Prideaux on the Deduction of the Dew-point 

 MEMORANDA. 



A series of Families in immediate and continuous affinity with each other, is 

 called an alliance, and is indicated by a termination in ales:— Ex. Osmundalet 

 are the Ferns. 



Parallel Alliances are called formations*, and are indicated by a termination 

 <u(r;— Ex. Lamiosae include Lamiales and Boraginales, the Nucamentosae of 

 Dr. Lindley. 



Series of successive alliances are called unions: — Ex. The Passifloral Union in- 

 cludes Violales, Passiflorales, and Homaliales, nearly'the Parietosae of Dr. Lindley. 

 [ ] Indicates that the order of succession among the families so included is not 



settled. 

 ( ) Indicates that the evidence for the station is more conflicting than usual. 

 f Indicates that the Family or Tribe may be compound. Tribes are occasion- 

 ally inserted to show transitions. 

 The Nomenclature of Dr. Lindley's System is usually taken as the standard. 



(1) Agardh's Fucoideae, nor idea;, ulvaceae, nostochinee, diatomere, confervoideee. 



(2) Here separated. 



(3) Link. 



(4) D. Don. 



(5) Jussieu. 



(6) Bartling. 

 (?) Arnott. 



(9) Chenopodiaceae here includes Scleranthaceae-amarantaceae-fchenopodiacew. 

 Phytolaccaceae includes Tetragoniaceae-phytolaccaceas-petiveriaceae. 

 Cytinaceae includes Rafflesiaceae. 



Cynaraceae — followed by (Xeranthemeae)-calendulaceze-arctotideac. 

 Asparagaceae includes ConvallarinaJ-parideae-asparageae-aloinae-anthericew. 

 Hemerocallaceae includes fScilleae-hemerocallideae-tulipeae. 

 Balanophoraceae includes Cynomoriaceae. 



XL Observations on the Deduction of the Dew-point from the 

 Indications of the Wet-bulb Thermometer, and on the Detec- 

 tion of minute quantities of foreign Matters diffused in the 

 Atmosphere ,• with Notices of Apparatus. By John Pri- 

 deaux, member of the Plymouth Institution ; in a letter to 

 Mr. Bray ley. 

 Dear Sir, 



THE wet-bulb thermometer, preferable to other hygrome- 

 ters from the permanence, directness, and simplicity of 

 its action, has the inconvenience of its indications being not 

 only subject to necessary calculations, but also, hitherto, to 

 considerable discrepancy in the principles on which these 

 computations are made; and to corresponding differences in 

 the resulting dew-points, even supported by irreconcileable 

 experiments. The pages of the Philosophical Magazine have 

 been so largely occupied in the discussion of these principles, 

 that it is not my intention to go much into them on the pre- 

 sent occasion ; on which I will offer little more than a compari- 

 son between Dr. Apjohn's table in vol. vii. p. 471, with that 

 of Dr. Mason in Thomso?i y s Records, vol. iv. p. 109. 



* A term used by Reichenbach. 



