21 
has found that by cultivating and so weakening the virus or 
poison of this disease he can vaccinate dogs or other animals, and 
so protect them from all danger of hydrophobia. Thus out of 88 
dogs, half of which were vaccinated and the other half not, that 
were bitten by 19 mad dogs, the unprotected animals all died of 
hydrophobia while the vaccinated speedly recovered. Whether 
we should any of us personally care to be so vaccinated on the 
chance of being some day bitten by a mad dog is a moot question, 
but all dogs exposed to this danger should be at any rate so pro- 
tected. When we think not only of the thousands of lives that 
have been saved and the myriads which may be, but the vast field 
of speculation and enquiry opened up to the Scientist and Physician 
by the patient labour of one man, we cannot fail to be struck with 
the advantage of special study. This is a question which interests 
not only doctors but the world at large, for if animals can be pro- 
tected by vaccination from Splenic fever, Fowl Cholera, and Rabies, 
may not mankind look forward to a time when they them- 
selves may be made secure by similar means from all 
diseases, such as Diphtheria, Scarlet Fever, Croup, Cholera, 
Consumption, &¢., which arise from germs? This then is one 
of the great problems of the day, and it seems in a fair way 
of being solved. But there is another problem which will also have to 
be solved, if not by this, certainly by the next generation, and 
that is the conservation of energy, the economy and utilisation of 
the enormous stores of now wasted power. For generations past 
we have been so in the habit of relying on the power generated by 
the combustion of coal, that we cannot, apparently, bring our 
minds to the contemplation of what is to be done when our coal 
measures are exhausted, which I need not say must happen sooner 
or later. Already we dig out from our English mines daily a mass 
of coal which if piled up would make a column 50ft. in diameter 
and 7,000 ft. high. JI need not tell the merest child that this 
quantity cannot be abstracted each day without causing, at no very 
distant date, a serious diminution, and finally, an exhaustion of our 
stores, however large. What then are we to do when our stock is 
expended. I need remind no member of this society that heat, 
light, motion, and electricity, are all forms of one and the same- 
force or energy, and that each is convertible into the other. Thus 
motivn may be made to become heat, as we know from the heating 
- of rapidly revolving axles, or when a cannon ball strikes an iron 
target producing heat, with or without a flash of light. A revolving 
electro-dynamo machine generates electricity, which may again be 
made to resolve itself into heat, motion, or light, and so on, in a 
never-ending cycle, But there must be always some form or other 
of force to start with. Ka nihilo nihil fit. Now it must have struck 
