406 Dr. 0. Herrmann — Distribution of GraptoUtcs. 



for cooking purposes, for boiling, and even baking, and Mr. G. 

 Maw, F.G.S., who describes the system, witnessed in a house three- 

 quarters of a mile from the boilers, a bucket of cold water raised to 

 boiling heat in three minutes by the passage of the steam through a 

 perforated nozzle plunged in the bucket. The operations of the 

 Heating Company have been up to the present time of an experi- 

 mental character, and from the 200 houses already supplied with the 

 heating connexion, the actual cost of the coal that would have been 

 used for heating has been provisionally received in payment, and the 

 amount has left a wide margin over the working expenses, though 

 the company's operations at present cover but a small portion of the 

 area for which they have provided plant." 



Tn conclusion, the man of science will no more doubt that supplies 

 of heat would be forthcoming from depths of 7000 or 8000 feet than 

 that water will be found in Chalk, or coal in the Coal-measures. 

 Whether London will ever be supplied with heat from this source is 

 a question apart ; but it needs no seer to pierce the not-distant future 

 when we shall be driven to every expedient to discover modes of 

 obtaining heat without the combustion of fuel, and the perhaps 

 far more remote future when we shall bore shafts down to the liquid 

 layer and conduct our smelting operations at the pit's mouth. 



III. — On the Distribution of the Graptolithid^ in Time and 



Space. 

 By Dr. Otto Herrmann.^ 



IT was indicated even by Murchison that the Graptolites constitute 

 admirable characteristic fossils of the Silurian formation. Sub- 

 sequent investigation has established that the group Graptolithidse is 

 essentially confined to the oldest fossiliferous formation. A single 

 genus, the genus Dictyograptus, Hopk. (Dictyonema, Hall), occupies 

 a remarkably exceptional position as regards its distribution in time. 

 Formerly, indeed, this genus was separated from the proper or true 

 Graptolites (Bhabdophora, Allraan), and referred with some other 

 genera (Dendrograjptus, Hall, Ftilogra'ptus, Hopk., Callogroptiis, Hall) 

 to the CampanularidEe ; but recently W. C. Brogger ^ has very clearly 

 shown that the genus in question differs very little from the true 

 Graptolites, inasmuch as the most important parts of the latter, such 

 as the sicula, and the hydrothecae, have been detected in it. By this 

 the Graptolithic nature of the genus in question is rendered very 

 probable. Members of the genus Dictyograptus, Hopk., appear 

 among the very oldest of known Graptolites ; the genus maintains 

 itself throughout the whole of the Silurian formation, while by its 



1 Dr. Herrmann has published in the " Nyt Magazin for Naturvidenskaberne," 

 vol. xxix. Heft. 2, the greater part of a treatise, in German, on the Graptolite family 

 Dichograptidas, the first chapter of which bears the above title, and is here translated. 

 This is terminated by an elaborate analytical bibliography of the literature of Grap- 

 tolites. The second chapter deals with the organization and economy of the Grapto- 

 lithida3, and the third (not yet completed) contains a monographic revision of the 

 genera and species of Dicliograptid?e. 



2 " Die silurischen Etagen 2 und 3 in Kristianiagebietund auf Eker," Christiania, 

 1882. 



