464 Proceedings of Philosophical Societies. [Dkc. 



sponds with the weight of an atom of it. Suppose now we want 

 to know how much oxygen combines with 200 mercury : bring 

 200 on the slide opposite to mercury on the scale ; then over 

 against oxygen on the slide will be found 16, the quantity of 

 oxygen required. Suppose we want to know how much oxide of 

 copper combines with 60 of sulphuric acid : bring sulphuric acid 

 opposite to 60, and we shall find over against oxide of copper 

 61, the number required. The Sliding Rule is fitted to answer 

 an infinite number of similar questions. 



Dr. Wollaston determined experimentally the composition of 

 nitrate of potash, and found it composed of 68 acid + 59 

 potash. His scale is referred to carbonate of lime, which he 

 considers as the most exact standard of comparison that can be 

 obtained. 



On Thursday, the 1 1 th of November, part of the Croonian 

 lecture on the influence of the Nervous System on Muscular 

 Motion, by B. C. Brodie, Esq. was read. This lecture began 

 with a short historical account of the facts and opinions of former 

 physiologists on this subject. The author then relates a number 

 of experiments which he himself instituted still farther to 

 advance the subject. He found that after the destruction of the 

 lower part of the spinal marrow of a dog, the arterial blood of 

 a horse injected into the lower extremities of the animal, after 

 circulating through the limb, came out at the mouths of the 

 veins dark coloured. He found that the lower extremities of a 

 frog, treated in the same way, though deprived of voluntary 

 motion, contracted by stimuli and by the galvanic influence. He 

 found that the heart of a rabbit continued to beat with its usual 

 regularity for some time after the blood-vessels had been emptied 

 of their contents ; but that the action of the heart was destroyed 

 when an animal was strangled, showing clearly that the stimulus 

 of the blood is not the exciting cause of the action of the heart. 



On Thursday, the 18th of November, the remainder of Mr. 

 Brodie's paper on the Influence of the Nervous System on Mus- 

 cular Motion, particularly of the Heart, was read. The author 

 concluded with some general inferences from the experiments 

 detailed in the preceding part of his paper. 



Some farther experiments, comparing the Gregorian and 

 Cassegrenian telescopes, by Brigade Major Cater, were also read. 

 The author related a new experiment which he had made, and 

 which confirmed the experiments detailed in his former paper on 

 the superiority of the Cassegrenian above the Gregorian tele- 

 scope. 



At the same meeting there was also read an analysis of a new 

 species of copper ore, from India, by Dr. Thomson. This ore 

 was discovered about 13 years ago by Dr. Heyne, at some dis- 



