PROCEEDINGS OF THE rOLTTECHNIC ASSOCIATION. 501 



any star visible to the eye can be found as I'eadily as the name and resi- 

 dence of a person in the directory. This is done by moving the index to 

 the proper place as regards the time of night and date of the month, and 

 if the sky is clear the name of every star visible can be told, and its time 

 of rising and setting, the rising and setting of the sun, &c. Mr. Withal! 

 explained its use in a very comprehensive manner. 



The Chairman. — Mr. Withall's planisphere, which he has just described, 

 has been shown to several scientific gentlemen, among them Prof. Pierce, 

 of Cambridge, who has approved of it; it is now in use in many of the 

 colleges, and is now adopted in many common schools. 



Mr. Grieves showed several specimens of peti'oleum from different wells, 

 and described their qualities. He said that it had been asserted that tur- 

 pentine was found in petrttleum, but in all his experiments he could not 

 find it. He was inclined to believe that the oils could be purified, and 

 that chlorine gas, which acts on the lower series, will be found best adapted 

 for this purpose. 



Owing to sickness, I have been unable to make the neccssar}^ arrange- 

 ments to show you some of the various products of the distillation of petro- 

 leum. And could I have done so, it could only have been done in a very 

 imperfect manner, as the time would not have admitted of more than one 

 product being eliminated, had I brought the crude petroleum ready treated 

 for distillation. Had that not been done we would not have been able to get 

 the first distillate. I would have been very happy indeed to have prepared 

 a few materials and shown some of their products had my health permitted 

 me to do so. 



I will first call your attention to two series of hydrurets or homologues 

 of two well known gases. The first is the "marsh" or light carburetted 

 hydrogen; the other is the "olefiant" or heavy carburetted h^'drogen. 

 Many of you are doubtless aware that every organic compound belongs to 

 some organic series in which each individual member of the elementar}^ sub- 

 stances is increased or diminished by certain regular and fixed quantities. 

 Petroleum, the subject matter of the evening, belongs to the second series 

 just alluded to, but not being a hydrocarbon oil proper, but a series of oils 

 belonging to the same family — the members of which are distinct one from 

 the other — they having the same root, but differing in the branches. Each 

 member of all the different groups containing a. different number of the 

 equivalents of C. and H., forming chains which rise step by step from the 

 solid to the liquid, and from a dense liquid to a light and extremely vola- 

 tile liquid, and finally to a permanent gas. When the components of 

 C. and H. are the same in any of the different groups, their properties 

 will be the same, irrespective of their origin. They will give the same 

 amount of light when burned in the same lamp. This likeness they may 

 possess can only be discovered by their boiling points, their specific gravi- 

 ties, or what is better still, their ultimate analyses. The species of hydro- 

 carbons includes oil gas, coal gas, olefiant gas, oil of lemons, otto of roses, 

 oil of turpentine, petroleum, naphtha, naphthaline, caoutchoucine, and sev- 

 eral others. 



Several of these, by distillation, yield hydrocarbons, isomeric, with 

 some of the series we get from distilling petroleum. In fact some of them 



